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Sample records for ni mn cr

  1. Cyclic and isothermal oxidation behavior at 1100 and 1200 C of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr alloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.

    1973-01-01

    Alloys of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr were cyclically oxidized at 1100 and 1200 C for up to 100 hours. Oxidation behavior was judged by sample thickness and weight change, metallography, diffraction, and microprobe analysis. The least attacked were Ni-40Cr and Ni-20Cr-3Si. The alloy Ni-20Cr-3Mn was much less attacked than Ni-20Cr, but more than the other alloys. The formation of Cr2O3 accounted for the increased resistance of Ni-Cr and Ni-20Cr-3Si, and the formation of MnCr2O4 accounts for the improvement in Ni-20Cr-3mn over Ni-20Cr.

  2. Experimental Study on Dynamic Mechanical Properties of 30CrMnSiNi2A Steel.

    NASA Astrophysics Data System (ADS)

    Huang, Fenglei; Yao, Wei; Wu, Haijun; Zhang, Liansheng

    2009-06-01

    Under dynamic conditions, the strain-rate dependence of material response and high levels of hydrostatic pressure cause the material behavior to be significantly different from what is observed under quasi-static condition. The curves of stress and strain of 30CrMnSiNi2A steel in different strain rates are obtained with SHPB experiments. Metallographic analyses show that 30CrMnSiNi2A steel is sensitive to strain rate, and dynamic compression leads to shear failure with the angle 45^o as the small carbide which precipitates around grain boundary changes the properties of 30CrMnSiNi2A steel. From the SHPB experiments and quasi-static results, the incomplete Johnson-Cook model has been obtained: σ=[1587+382.5(ɛ^p)^0.245][1+0.017ɛ^*], which can offer parameters for theory application and numerical simulation.

  3. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  4. High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy

    SciTech Connect

    Tawancy, H.M.

    1996-04-01

    An investigation was carried out to study the kinetics and products of oxidation of a wrought Ni-Cr-W-Mn-Si-La alloy at temperatures in the range of 950 to 1150{degrees}C. Oxidation kinetics were evaluated from measurements of weight change, metal loss, and internal penetration. Analytical electron microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction were used to characterize the scale microstructure. Initially, La was observed to segregate within a surface layer of about 5 {mu}m thick, which promoted selective oxidation of Cr and Mn. Oxidation kinetics were found to follow a parabolic-rate law with an activation energy of about 232 kJ/mol. During steady-state oxidation, the scale consisted of an inner adherent layer of {alpha}-Cr{sub 2}O{sub 3} modified by the presence of La and Si, and shielded by an outer layer of MnCr{sub 2}O{sub 4}. Most of the La was segregated to grain boundaries of the {alpha}-Cr{sub 2}O{sub 3} scale, however, Si was homogeneously distributed. It was concluded that the characteristic oxidation resistance of the alloy was related to the synergistic effects of Ni and Cr and to the effective minor additions of La, Si, and Mn; however, the useful life of the scale was limited by rupture and surface depletion in Cr, leading to accelerated internal oxidation.

  5. Investigation of Modified Ni-Cr-Mn Base Alloys for SOFC Interconnect Applications

    SciTech Connect

    Yang, Z Gary; Singh, Prabhakar; Stevenson, Jeffry W.; Xia, Gordon

    2006-09-01

    Two Ni-Cr-W-Mn base alloys based on Haynes 230 were developed and evaluated against criteria relevant to SOFC interconnect applications, which included oxidation behavior under SOFC operating conditions, scale electrical conductivity, and thermal expansion. It was found that, similar to the ferritic stainless steel Crofer22 APU, additions of Mn led to the formation of a unique scale that was comprised of a M3O4 (M=Mn, Cr, Ni, …) spinel-rich top layer and Cr2O3-rich sub-layer. The modified alloys demonstrated reasonable oxidation resistance under SOFC operating conditions, though the Mn additions increased the scale growth rate and thus sacrificed to some extent the oxidation resistance of the base alloy (Haynes 230). The formation of a spinel-rich top layer improved the scale conductivity, especially during the early stages of oxidation, but the higher scale growth rate resulted in a higher rate of increase in the area-specific electrical resistance. Due to their FCC crystal structure, the Ni-Cr-W-Mn base alloys demonstrated a CTE that was higher than that of anode-supported cells and candidate ferritic stainless steels such as Crofer22 APU.

  6. Naturally Occurring Cr and Ni in the Sacramento Valley: II. Mn Oxides and the Mobility of Cr(VI) and Ni

    NASA Astrophysics Data System (ADS)

    Mills, C. T.; Morrison, J. M.; Goldhaber, M. B.; Foster, A. L.; Wolf, R. E.; Wanty, R. B.

    2007-12-01

    Soil manganese oxides can strongly affect the mobility and redox state of several toxic trace metals. We are studying the biogeochemical origin of Mn oxides and their association with Cr and Ni in soils of the Sacramento Valley, California. Both Cr and Ni are likely derived from ultramafic rocks that underlie Coast Range drainages to the west of the study area. The impact of weathering and erosion of these rocks is evident in the high levels of total Cr (80 to 1420 μg g-1) and nickel (65 to 224 μg g-1) that occur broadly in western Sacramento Valley soils. Although much of the Cr is bound in refractory spinels as Cr(III), some mobilization of Cr is apparent in the coincidence of enriched soils with high contents of Cr(VI) in ground water. Data from the National Water Information System (NWIS) shows 7 of 12 sampled wells within a 600 km2 area in the Sacramento Valley having Cr(VI) concentrations between 60 and 100% of the CA maximum contaminant level for drinking water (50 μg l-1). A 3-meter depth soil profile collected within the lower Putah Creek watershed was examined to investigate processes contributing to the oxidation and mobilization of natural Cr(III). Hydroxylamine hydrochloride-reducible Mn was determined for 8 depth intervals as a measure of manganese oxide occurrence. Concentrations of reducible Mn varied between 360 and 690 μg g-1 with depth and peaked at 2.7 m below the surface. Concentrations of anion exchangeable Cr(VI) were as high as 6 ng g-1 and were positively correlated (r2=0.59; p=0.07) with reducible Mn. Scanning electron microscopy of soil minerals from the 2.9 to 3.0 m interval showed Cr-bearing spinel grains enclosed within Mn oxide micro concretions suggesting a potential mechanism for the oxidation of natural Cr(III) to mobile Cr(VI). Consistent with the known tendency of Ni to sorb on Mn oxides, substantial Ni (13 to 45 μg g-1) was released in the reducible Mn fraction and it strongly correlates (r2=0.76; p=0.005) with reducible Mn

  7. Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

    NASA Astrophysics Data System (ADS)

    Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

    2015-02-01

    High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

  8. Effect of Manganese on Microstructures and Solidification Modes of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Wen, Yuhua; Du, Yangyang; Yu, Qinxu; Yang, Qin

    2013-10-01

    We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we examined whether the Creq/Nieq equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software® together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software® together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Creq/Nieq equation should be developed or the thermodynamic database of Thermo-Calc software® should be corrected.

  9. Mechanical Properties and Microstructure of the CoCrFeMnNi High Entropy Alloy Under High Strain Rate Compression

    NASA Astrophysics Data System (ADS)

    Wang, Bingfeng; Fu, Ao; Huang, Xiaoxia; Liu, Bin; Liu, Yong; Li, Zezhou; Zan, Xiang

    2016-07-01

    The equiatomic CoCrFeMnNi high entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was prepared by the spark plasma sintering technique. Dynamic compressive tests of the CoCrFeMnNi high entropy alloy were deformed at varying strain rates ranging from 1 × 103 to 3 × 103 s-1 using a split-Hopkinson pressure bar (SHPB) system. The dynamic yield strength of the CoCrFeMnNi high entropy alloy increases with increasing strain rate. The Zerilli-Armstrong (Z-A) plastic model was applied to model the dynamic flow behavior of the CoCrFeMnNi high entropy alloy, and the constitutive relationship was obtained. Serration behavior during plastic deformation was observed in the stress-strain curves. The mechanism for serration behavior of the alloy deformed at high strain rate is proposed.

  10. Mechanical Properties and Microstructure of the CoCrFeMnNi High Entropy Alloy Under High Strain Rate Compression

    NASA Astrophysics Data System (ADS)

    Wang, Bingfeng; Fu, Ao; Huang, Xiaoxia; Liu, Bin; Liu, Yong; Li, Zezhou; Zan, Xiang

    2016-05-01

    The equiatomic CoCrFeMnNi high entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was prepared by the spark plasma sintering technique. Dynamic compressive tests of the CoCrFeMnNi high entropy alloy were deformed at varying strain rates ranging from 1 × 103 to 3 × 103 s-1 using a split-Hopkinson pressure bar (SHPB) system. The dynamic yield strength of the CoCrFeMnNi high entropy alloy increases with increasing strain rate. The Zerilli-Armstrong (Z-A) plastic model was applied to model the dynamic flow behavior of the CoCrFeMnNi high entropy alloy, and the constitutive relationship was obtained. Serration behavior during plastic deformation was observed in the stress-strain curves. The mechanism for serration behavior of the alloy deformed at high strain rate is proposed.

  11. Corrosion Behavior of Thermally Sprayed NiCrBSi Coating on 16MnR Low-Alloy Steel in KOH Solution

    NASA Astrophysics Data System (ADS)

    Zeng, Q.; Sun, J.; Emori, W.; Jiang, S. L.

    2016-05-01

    NiCrBSi coatings were selected as protective material and air plasma-sprayed on 16MnR low-alloy steel substrates. Corrosion behavior of 16MnR substrates and NiCrBSi coatings in KOH solution were evaluated by polarization resistance ( R p), potentiodynamic polarization curves, electrochemical impedance spectroscopy, and immersion corrosion tests. Electrolytes were solutions with different KOH concentrations. NiCrBSi coating showed superior corrosion resistance in KOH solution compared with the 16MnR. Corrosion current density of 16MnR substrate was 1.7-13.0 times that of NiCrBSi coating in the given concentration of KOH solution. By contrast, R p of NiCrBSi coating was 1.2-8.0 times that of the substrate, indicating that the corrosion rate of NiCrBSi coating was much lower than that of 16MnR substrate. Capacitance and total impedance value of NiCrBSi coating were much higher than those of 16MnR substrate in the same condition. This result indicates that corrosion resistance of NiCrBSi coating was better than that of 16MnR substrate, in accordance with polarization results. NiCrBSi coatings provided good protection for 16MnR substrate in KOH solution. Corrosion products were mainly Ni/Fe/Cr oxides.

  12. Influence of Carbon on the Microstructure of a Fe-Mn-Si-Cr-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Mostafa, Khaled M.; de Baerdemaeker, J.; van Caenegem, N.; Segers, D.; Houbaert, Y.

    2009-08-01

    The influence of the addition of C to the Fe-Mn-Si-Cr-Ni base material is investigated at room temperature. Steel samples were deformed during a tensile experiment up to a strain of 17%. Light optical microscopy (OM) and x-ray diffraction (XRD) gave information about the different micro-structural phases that exist in the deformed and the undeformed alloys. The evolution of the defect structure is followed by positron annihilation techniques such as Doppler broadening of annihilation radiation spectroscopy (DBAR) and the positron annihilation lifetime spectroscopy (PALS). During deformation a martensitic ɛ-phase is induced. The size of the martensite plates increases with increasing deformation.

  13. Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Chelariu, R.; Popescu, G.; Carcea, I.

    2016-06-01

    In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

  14. Synthesis of Waste Form in the Gd-Fe-Al-Ni-Mn-Cr-O System

    SciTech Connect

    Chae, S.C.; Jang, Y.N.; Bae, I.K.; Ryu, K.W.

    2006-07-01

    Poly-phase waste form which was the mixture of Gd{sub 3}Fe{sub 2}Al{sub 3}O{sub 12} and (Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4} was synthesized. Also, we are intended to examine phase relation and physicochemical properties of coexisted phases in the compositions and to confirm accommodation relation of elements and phases. Two types of phase series were observed: Garnet-perovskite-spinel and Garnet-spinel. The compositions of garnets and spinels were nonstoichiometric, and especially, this poly-phase ceramics may be in a good waste form. The excessive Gd in garnets indicated the immobilization of higher content of actinides. The nonstoichiometric compositions of garnet and spinel were attributed to the formation of perovskite in that perovskite contained Gd, Fe and Al from garnet and Cr from spinel. (authors)

  15. Lattice dynamics in austenitic stainless steels Fe 18Cr 12Ni 2Mo and Fe 18Cr 16Ni 10Mn

    NASA Astrophysics Data System (ADS)

    Rajevac, V.; Hoelzel, M.; Danilkin, S. A.; Hoser, A.; Fuess, H.

    2004-04-01

    Phonon dispersion curves of austenitic stainless steels Fe-18Cr-16Ni-10Mn and Fe-18Cr-12Ni-2Mo have been measured by triple-axis neutron spectroscopy. The data were analysed using Born-von Karman interactions as well as calculations including the contribution of conduction electrons on the lattice dynamics. An appropriate description of the experimental data was obtained by taking into account two-neighbour shells plus the contribution of the electron gas. The elastic constants and moduli obtained are close to reported results by ultrasonic studies on polycrystalline samples. The phonon densities of states in both systems calculated from the dispersion curves agree well with results obtained by time-of-flight neutron spectroscopy on polycrystalline samples. The Debye temperature THgr(T) shows a minimum around 40 K, similar to copper and nickel.

  16. Nanomechanical Behavior of CoCrFeMnNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Mridha, Sanghita; Das, Santanu; Aouadi, Samir; Mukherjee, Sundeep; Mishra, Rajiv S.

    2015-08-01

    The nanomechanical behavior of the Co20Cr20Fe20Mn20Ni20 high-entropy alloy was investigated in as-cast, rolled, annealed, and thin-film forms. Dislocation nucleation was studied by repeated indents at a low load for each of the different processing conditions. Distinct displacement bursts (pop in) were observed in the loading curve marked by incipient plasticity for all the samples. The as-cast and annealed samples showed pop ins for 100% of the indents, whereas the rolled and thin-film samples showed a much lower fraction of displacement bursts. This was explained by the high density of dislocations for the cold-worked and thin-film conditions. The strong depth dependence of hardness was explained by geometrically necessary dislocations. The nanomechanical behavior and twinned microstructure indicate low stacking-fault energy for this high-entropy alloy.

  17. Mechanical cycling effects at Fe-Mn-Si-Cr-Ni SMAs obtained by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Pricop, B.; Söyler, U.; Comčneci, R. I.; Özkal, B.; Bujoreanu, L. G.

    Specimens from Fe-Mn-Si-Cr-Ni SMA, obtained by powder metallurgy and compacted through hot rolling, were subjected to tensile loading-unloading cycles. The pseudoelastic parameters were determined based on recorded stress-strain curves, and their variation tendency with increasing the number of mechanical cycles was discussed. The gauges of tensile specimens were cut after mechanical cycling and were subjected to structural and dilatometric analysis. The structure was analyzed by XRD and SEM, aiming to reveal mechanical cycling effects. The thermomechanical response on heating, of mechanically cycled specimens, was recorded by dilatometry and revealed a tendency to enhance thermal expansion as an effect of increasing the number of cycles. The microstructural changes, induced by mechanical cycling, consisted in the stress induced formation of α' martensite.

  18. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    DOE PAGESBeta

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with amore » composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.« less

  19. An experimental and thermodynamic equilibrium investigation of the Pb, Zn, Cr, Cu, Mn and Ni partitioning during sewage sludge incineration.

    PubMed

    Liu, Jingyong; Fu, Jiewen; Ning, Xun'an; Sun, Shuiyu; Wang, Yujie; Xie, Wuming; Huang, Shaosong; Zhong, Sheng

    2015-09-01

    The effects of different chlorides and operational conditions on the distribution and speciation of six heavy metals (Pb, Zn, Cr, Cu, Mn and Ni) during sludge incineration were investigated using a simulated laboratory tubular-furnace reactor. A thermodynamic equilibrium investigation using the FactSage software was performed to compare the experimental results. The results indicate that the volatility of the target metals was enhanced as the chlorine concentration increased. Inorganic-Cl influenced the volatilization of heavy metals in the order of Pb>Zn>Cr>Cu>Mn>Ni. However, the effects of organic-Cl on the volatility of Mn, Pb and Cu were greater than the effects on Zn, Cr and Ni. With increasing combustion temperature, the presence of organic-Cl (PVC) and inorganic-Cl (NaCl) improved the transfer of Pb and Zn from bottom ash to fly ash or fuse gas. However, the presence of chloride had no obvious influence on Mn, Cu and Ni. Increased retention time could increase the volatilization rate of heavy metals; however, this effect was insignificant. During the incineration process, Pb readily formed PbSiO4 and remained in the bottom ash. Different Pb compounds, primarily the volatile PbCl2, were found in the gas phase after the addition of NaCl; the dominant Pb compounds in the gas phase after the addition of PVC were PbCl2, Pb(ClO4)2 and PbCl2O4. PMID:26354691

  20. Hot and cold rolling of high nitrogen Cr-Ni and Cr-Mn austenitic stainless steels

    SciTech Connect

    Iiola, R.; Hanninen, H.; Kauppi, T.

    1998-10-01

    Behavior of austenitic Cr-Ni-(0.14--0.50)N and Cr-Mn-(0.78--1.00)N steels in hot and cold rolling was investigated by rolling experiments and mechanical testing. Structure of the steels in the as-cast condition and fracture surfaces after the rolling experiments were investigated using optical and scanning electron microscopy (SEM). Resistance to deformation was calculated using rolling forces in hot rolling. Increase in strength in the rolling experiments was related to the nitrogen content of the steels. Resistance to deformation during hot rolling increased with decreasing rolling temperature and with increasing nitrogen content. In some steels, hot rolling led to edge cracking, which was more a function of impurity than nitrogen content. Microscopy revealed that the edge cracking occurred along grain boundaries and second phase particles. For the cold-rolled steels, the highest achievable reductions were limited due to a crocodiling phenomenon, that is, opening of the strip end. Fracture type at the opened strip end was a brittle-like fracture.

  1. Examination of Multiphase (Zr,Ti)(V,Cr,Mn,Ni)2 Ni-MH Electrode Alloys: Part II. Solid-State Transformation of the Interdendritic B2 Phase

    NASA Astrophysics Data System (ADS)

    Bendersky, L. A.; Wang, K.; Boettinger, W. J.; Newbury, D. E.; Young, K.; Chao, B.

    2010-08-01

    Solidification microstructure of multicomponent (Zr,Ti)-Ni-(V,Cr,Mn,Co) alloys intended for use as negative electrodes in Ni-metal hydride (Ni-MH) batteries was studied in Part I of this series of articles. Part II of the series examines the complex internal structure of the interdendritic grains formed by solid-state transformation and believed to play an important role in the electrochemical charge/discharge characteristics of the overall alloy composition. By studying one alloy, Zr21Ti12.5V10Cr5.5Mn5.1Co5.0Ni40.2Al0.5Sn0.3, it is shown that the interdendritic grains solidify as a B2 (Ti,Zr)44(Ni,TM)56 phase, and then undergo transformation to Zr7Ni10-type, Zr9Ni11-type, and martensitic phases. The transformations obey orientation relationships between the high-temperature B2 phase and the low-temperature Zr-Ni-type intermetallics, and consequently lead to a multivariant structure. The major orientation relationship for the orthorhombic Zr7Ni10 type is [011]Zr7Ni10//[001]B2; (100)Zr7Ni10//(100)B2. The orientation relationship for the tetragonal Zr9Ni11 type is [001]Zr9Ni11//[001]B2; (130)Zr9Ni11//(100)B2. Binary Ni-Zr and ternary Ti-Ni-Zr phase diagrams were used to rationalize the formation of the observed domain structure.

  2. The Effects of Helium Bubble Microstructure on Ductility in Annealed and HERF 21Cr-6Ni-9Mn Stainless Steel

    SciTech Connect

    Tosten, M.H.; Morgan, M.J.

    1998-01-01

    This study examined the effects of microstructure on the ambient temperature embrittlement from hydrogen isotopes and decay helium in 21Cr-6Ni-9Mn stainless steel. Hydrogen and tritium-exposed 21Cr-6Ni-9Mn stainless steel tensile samples were pulled to failure and then characterized by transmission electron microscopy (TEM) and optical microscopy. This study determined that ductility differences between annealed and high-energy-rate-forged (HERF) stainless steel containing tritium and its decay product, helium, could be related to differences in the helium bubble microstructures. The HERF microstructures were more resistant to tritium-induced embrittlement than annealed microstructures because the high number density of helium bubbles on dislocations trap tritium within the matrix and away from the grain boundaries.

  3. Microstructure and shape recovery characteristics in a TIG-welded Fe-Mn-Si-Cr-Ni shape memory alloy

    NASA Astrophysics Data System (ADS)

    Qiao, Zhixia; Li, Lianjin; Wang, Dongai; Li, Zongmin

    2007-07-01

    Microstructure of an Fe-Mn-Si-Cr-Ni shape memory alloy (SMA) after being TIG (tungsten-insert gas welding) welded was investigated using scanning electron microscope (SEM) and X-ray diffractometer. The results show that dendrite crystals composed of cellular sub-structures form in the weld zone due to remelting. There is no obvious change in microstructure of the heat-affected zone (HAZ) except for some degree of growth of austenite grains. Since both the weld zone and HAZ consist of single phase of austenite (γ), pre-strain can still induce the γ-->ɛ martensite transformation in welding joints of the alloy. Effect of TIG welding on shape recovery characteristics of the alloy was examined by bending tests and it was found that the TIG-welded Fe-Mn-Si-Cr-Ni alloy exhibits almost the same excellent SME as the base material.

  4. Microstructure and Mechanical Properties After Shock Wave Loading of Cast CrMnNi TRIP Steel

    NASA Astrophysics Data System (ADS)

    Eckner, Ralf; Krüger, L.; Ullrich, C.; Rafaja, D.; Schlothauer, T.; Heide, G.

    2016-08-01

    The mechanical response of shock wave-prestrained high-alloy Cr16-Mn7-Ni6 TRIP steel was investigated under compressive and tensile loading at room temperature. Previous shock wave loading was carried out using a flyer-plate assembly with different amounts of explosives in order to achieve shock pressures of 0.3, 0.6, 0.9, and 1.2 Mbar. A significant increase in hardness and strength was observed as compared with the initial as-cast condition. In contrast, a slight decrease in strain hardening rates was measured together with a decrease in fracture elongation in the tensile test. Microstructural analyses of the shock-loaded samples were performed by light optical and scanning electron microscopy. The microstructure revealed a high density of deformation bands consisting of separated stacking faults, ɛ-martensite, or twins. Significant amounts of deformation-induced α'-martensite were only present at the highest shock pressure of 1.2 Mbar. The thickness of the deformation bands and the number of martensite nuclei at their intersections increased with increasing shock pressure. In all shock-loaded specimens, pronounced phase transformation occurred during subsequent mechanical testing. Consequently, the amount of the deformation-induced α'-martensite in the shock-loaded specimens was higher than in the unshocked as-cast samples.

  5. Factors Affecting the Hydrogen Embrittlement Resistance of Ni-Cr-Mn-Nb Welds

    SciTech Connect

    G.A. Young; C.K. Battige; N. Liwis; M.A. Penik; J. Kikel; A.J. Silvia; C.K. McDonald

    2001-03-18

    Nickel based alloys are often welded with argon/hydrogen shielding gas mixtures to minimize oxidation and improve weld quality. However, shielding gas mixtures with {ge} 1% hydrogen additions can result in hydrogen concentrations greater than 5 wt. ppm in the weld metal and reduce ductility via hydrogen embrittlement. For the conditions investigated, the degree of hydrogen embrittlement is highly variable between 5 and 14 wt. ppm. investigation of hydrogen embrittlement of EN82H GTAW welds via tensile testing, light microscopy, transmission electron microscopy, orientation imaging microscopy, and thermal desorption spectroscopy shows that this variability is due to the inhomogeneous microstructure of the welds, the presence of recrystallized grains, and complex residual plastic strains. Specifically, research indicates that high residual strains and hydrogen trapping lower the ductility of Ni-Cr-Mn-Nb weld metal when dissolved hydrogen concentrations are greater than 5 wt. ppm. The inhomogeneous microstructure contains columnar dendritic, cellular dendritic, and recrystallized grains. The decreased tensile ductility observed in embrittled samples is recovered by post weld heat treatments that decrease the bulk hydrogen concentration below 5 wt. ppm.

  6. Electrokinetic recovery of Cd, Cr, As, Ni, Zn and Mn from waste printed circuit boards: effect of assisting agents.

    PubMed

    Xiu, Fu-Rong; Zhang, Fu-Shen

    2009-10-15

    The printed circuit boards (PCBs) contains large number of heavy metal such as Cd, Cr, As, Ni, Zn and Mn. In this study, the use of electrokinetic (EK) treatment with different assisting agents has been investigated to recover the heavy metals from waste PCBs, and the effectiveness of different assisting agents (HNO(3), HCl, citric acid) was evaluated. The PCBs were first pre-treated by supercritical water oxidation (SCWO) process, then subjected to EK process. The heavy metal speciation, migration and recovery efficiency in the presence of different assisting agents during EK process were discussed. The mass loss of Cd, Cr, As and Zn during the SCWO process was negligible, but approximately 52% of Ni and 56% of Mn were lost in such a process. Experimental results showed that different assisting agents have significant effect on the behavior and recovery efficiency of different heavy metals. HCl was highly efficient for the recovery of Cd in waste PCBs due to the low pH and the stable complexation of Cl(-). Citric acid was highly efficient for the recovery of Cr, Zn and Mn. HNO(3) was low efficient for recovery of most heavy metals except for Ni. PMID:19481346

  7. Sediment fractionation of Cu, Ni, Zn, Cr, Mn, and Fe in one experimental and three natural marshes

    SciTech Connect

    Lindau, C.W.; Hossner, L.R.

    1982-07-01

    Dredged sediments from the Gulf Intracoastal Waterway near Galveston, Tex., were used as a substrate material in the construction of an experimental intertidal salt marsh. Selected substrate properties were compared with those of established marshes. Clay mineralogical properties of the experimental marsh were compared with those of three nearby natural marshes. A sequential chemical extraction procedure was used to obtain data on the partitioning of micronutrients and heavy metals among selected marsh substrate fractions. Clay minerals found in the sediments of the experimental marsh were equivalent to those identified in the natural marshes. Total elemental substrate concentrations of Cu, Ni, Cr, Zn, Mn, and Fe averaged 7.9, 8.6, 25.5, 25.2, 123, and 12,200 ..mu..g/g, respectively, over the four marsh sites. Copper, nickel, zinc, and chromium displayed only minor variations in substrate partitioning between the experimental and natural marsh samples. Micronutrients and heavy metal concentrations in the exchangeable and water-soluble fraction were low compared with other fractions. Approximately 30% of the total substrate Cu, Ni, and Zn was associated with the organic matter fraction. Metals fixed within the lattice structures of clay and silicate minerals ranged from 20% Mn for experimental marsh samples to 90% Cr for one of the natural marshes. Major differences in Mn and Fe substrate partitioning were observed when the experimental marsh samples were compared with those of the natural marshes.

  8. Influence of Temperature on Fatigue-Induced Martensitic Phase Transformation in a Metastable CrMnNi-Steel

    NASA Astrophysics Data System (ADS)

    Biermann, Horst; Glage, Alexander; Droste, Matthias

    2016-01-01

    Metastable austenitic steels can exhibit a fatigue-induced martensitic phase transformation during cyclic loading. It is generally agreed that a certain strain amplitude and a threshold of the cumulated plastic strain must be exceeded to trigger martensitic phase transformation under cyclic loading. With respect to monotonic loading, the martensitic phase transformation takes place up to a critical temperature—the so-called M d temperature. The goal of the present investigation is to determine an M d,c temperature which would be the highest temperature at which a fatigue-induced martensitic phase transformation can take place. For this purpose, fatigue tests controlled by the total strain were performed at different temperatures. The material investigated was a high-alloy metastable austenitic steel X3CrMnNi16.7.7 (16.3Cr-7.2Mn-6.6Ni-0.03C-0.09N-1.0Si) produced using the hot pressing technique. The temperatures were set in the range of 283 K (10 °C) ≤ T ≤ 473 K (200 °C). Depending on the temperature and strain amplitude, the onset of the martensitic phase transformation shifted to different values of the cumulated plastic strain, or was inhibited completely. Moreover, it is known that metastable austenitic CrMnNi steels with higher nickel contents can exhibit the deformation-induced twinning effect. Thus, at higher temperatures and strain amplitudes, a transition from the deformation-induced martensitic transformation to deformation-induced twinning takes place. The fatigue-induced martensitic phase transformation was monitored during cyclic loading using a ferrite sensor. The microstructure after the fatigue tests was examined using the back-scattered electrons, the electron channeling contrast imaging and the electron backscatter diffraction techniques to study the temperature-dependent dislocation structures and phase transformations.

  9. Processing, Microstructure and Mechanical Properties of the CrMnFeCoNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Gludovatz, Bernd; George, Easo P.; Ritchie, Robert O.

    2015-08-01

    Equiatomic multi-component alloys, referred to variously as high-entropy alloys, multi-component alloys, or compositionally complex alloys in the literature, have recently received significant attention in the materials science community. Some of these alloys can display a good combination of mechanical properties. Here, we review recent work on the processing, microstructure and mechanical properties of one of the first and most studied high-entropy alloys, namely the single-phase, face-centered cubic alloy CrMnFeCoNi, with emphasis on its excellent damage tolerance (strength with toughness) in the temperature range from room temperature down to liquid nitrogen temperature.

  10. Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels

    NASA Astrophysics Data System (ADS)

    Mahmudi, Abbas; Nedjad, Syamak Hossein; Behnam, Mir Masud Jabbari

    2011-10-01

    Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied. To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used. The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2(Mo, Ti) Laves phase particles, which are stable at high temperatures. These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment.

  11. Study of the effect of annealing on defects in Fe Mn Si Cr Ni C alloy by slow positron beam

    NASA Astrophysics Data System (ADS)

    Mostafa, Khaled. M.; De Baerdemaeker, J.; Van Caenegem, N.; Segers, D.; Houbaert, Y.

    2008-10-01

    FeMnSi shape memory alloys (SMAs) have received much attention as one-way SMAs due to their cost-effectiveness. Variable-energy (0-30 keV) positron beam studies have been carried out on a Fe-Mn-Si-Cr-Ni-C alloy with different degrees of deformation. Doppler broadening profiles of the positron annihilation as a function of incident positron energy were shown to be quite sensitive to defects introduced by deformation. The variation of the nature and the concentration of defects are studied as a function of isochronal annealing temperature. These results are correlated with the data measured with the positron annihilation lifetime spectroscopy (PALS). The positron annihilation results are compared to XRD and optical microscopy (OM).

  12. Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems.

    PubMed

    Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

    2016-01-01

    In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy. PMID:26923713

  13. Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems

    PubMed Central

    Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

    2016-01-01

    In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy. PMID:26923713

  14. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    SciTech Connect

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials can be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.

  15. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  16. Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

    DOE PAGESBeta

    Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

    2015-06-14

    Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials canmore » be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.« less

  17. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  18. Abrasive resistance of metastable V-Cr-Mn-Ni spheroidal carbide cast irons using the factorial design method

    NASA Astrophysics Data System (ADS)

    Efremenko, V. G.; Shimizu, K.; Cheiliakh, A. P.; Pastukhova, T. V.; Chabak, Yu. G.; Kusumoto, K.

    2016-06-01

    Full factorial design was used to evaluate the two-body abrasive resistance of 3wt%C-4wt%Mn-1.5wt%Ni spheroidal carbide cast irons with varying vanadium (5.0wt%-10.0wt%) and chromium (up to 9.0wt%) contents. The alloys were quenched at 920°C. The regression equation of wear rate as a function of V and Cr contents was proposed. This regression equation shows that the wear rate decreases with increasing V content because of the growth of spheroidal VC carbide amount. Cr influences the overall response in a complex manner both by reducing the wear rate owing to eutectic carbides (M7C3) and by increasing the wear rate though stabilizing austenite to deformation-induced martensite transformation. This transformation is recognized as an important factor in increasing the abrasive response of the alloys. By analyzing the regression equation, the optimal content ranges are found to be 7.5wt%-10.0wt% for V and 2.5wt%-4.5wt% for Cr, which corresponds to the alloys containing 9vol%-15vol% spheroidal VC carbides, 8vol%-16vol% M7C3, and a metastable austenite/martensite matrix. The wear resistance is 1.9-2.3 times that of the traditional 12wt% V-13wt% Mn spheroidal carbide cast iron.

  19. The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

  20. First-principles study on the magnetism and electronic structure in 3d transition metal (X=Sc, V, Cr, Mn, Fe, Ni, Cu) doped CoO

    NASA Astrophysics Data System (ADS)

    Liu, R. X.; Wang, X. C.; Chen, G. F.; Yang, B. H.

    2016-03-01

    We have studied the electronic structure and magnetism of the single transitional metal element X=Sc, V, Cr, Mn, Fe, Ni, Cu-doped CoO systems by first-principles calculations. At X=Sc, Cr, Cu, the binding energy of the doped systems is lower than pure CoO, suggesting that these systems are energetically stable. In the Sc, V, Cr, Mn, Fe, Ni, Cu-doped 2×2×2 CoO supercells, the total magnetic moments are 3.03, 5.64, 6.80, 7.70, 6.93, 2.30 and 1.96 μB, respectively. At X=Cr and Fe, the doped CoO systems are half-metallic with a high spin polarization. The large magnetic moment and high spin polarization in the Cr and Fe-doped CoO are important for the design of the spintronic devices.

  1. Electronic structures of the ferrimagnetic double-perovskites Sr2XReO6 (X = Cr, Mn, Fe, Ni) with the modified Becke-Johnson potential

    NASA Astrophysics Data System (ADS)

    Guo, San-Dong

    2015-04-01

    We investigate the electronic structures and magnetic properties of the ferrimagnetic double-perovskites Sr2XReO6 (X = Cr, Mn, Fe, Ni) by using Tran and Blaha's modified Becke and Johnson exchange potential. The calculated results show that Sr2XReO6 (X = Cr, Fe) are half-metals, and Sr2XReO6 (X = Mn, Ni) are insulators, which is in accordance with the experimental results. By using the ionic picture, we explain the trend in the density of states and total magnetic moment with X changing from Cr to Ni. We find that the insulating property is associated with X2 +, while the metallic character is associated with X3 +. The Re t2g splitting in the minority channel leads to insulativity of Sr2XReO6 (X = Mn, Ni), and the Re t2g splitting of Sr2MnReO6 is caused by lattice distortion, while Sr2NiReO6's splitting is due to the heavier atomic mass of Ni. When spin-orbit coupling is included, the spin polarization of Sr2XReO6 (X = Cr, Fe) drifts off 100%, and the related gaps of Sr2XReO6 (X = Mn, Ni) become narrow. The spin-orbit coupling results in a significant increase in the total magnetic moment due to an unquenched Re orbital moment. Our calculated energy band structures show that Sr2MnReO6 is a spin gapless semiconductor, which can realize fully polarized spin-down electrons and spin-up holes.

  2. Effect of Pre-straining on the Shape Recovery of Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Maji, Bikas C.; Krishnan, Madangopal; Verma, Amit; Basu, R.; Samajdar, I.; Ray, Ranjit K.

    2015-02-01

    The effect of pre-straining on the shape recovery behavior of Fe-14Mn-6Si-9Cr-5Ni (wt pct) shape memory alloy (SMA) has been studied. The shape recovery associated with the reverse ɛ martensitic transformation, i.e., ɛ → γ, was characterized by dilatometry using specimens which were pre-strained to different extent (0 to 14 pct). Dilatometric studies revealed that in Fe-Mn-Si-Cr-Ni SMA, the shape recovery takes place in two stages: (i) in the first stage, the unpinned fraction of stress-induced ɛ martensite reverts back to parent phase γ in the temperature regime of 353 K to 653 K (80 °C to 380 °C) and (ii) in the second stage the remaining "pinned" ɛ martensite is unpinned by the decomposition of deformation-induced α' martensite in the temperature range of 743 K to 893 K (470 °C to 620 °C). The amount of recovery in the first stage decreases with pre-strain, whereas it increases in the second stage. The ɛ → γ transformation finish temperature, A f, increases with increase in pre-strain amount, though the reverse transformation start temperature, A S, remains unaffected. Microstructural characterization revealed that the amount of deformation-induced α' martensite depends on the mode of straining and the crystallographic texture of the starting material. The reversion of α' martensite is seen to occur by the precipitation of Fe5Ni3Si2-type intermetallic π-phase within these plates.

  3. Exact ab initio transport coefficients in bcc Fe-X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

    NASA Astrophysics Data System (ADS)

    Messina, Luca; Nastar, Maylise; Garnier, Thomas; Domain, Christophe; Olsson, Pär

    2014-09-01

    Defect-driven diffusion of impurities is the major phenomenon leading to formation of embrittling nanoscopic precipitates in irradiated reactor pressure vessel (RPV) steels. Diffusion depends strongly on the kinetic correlations that may lead to flux coupling between solute atoms and point defects. In this work, flux coupling phenomena such as solute drag by vacancies and radiation-induced segregation at defect sinks are systematically investigated for six bcc iron-based dilute binary alloys, containing Cr, Cu, Mn, Ni, P, and Si impurities, respectively. First, solute-vacancy interactions and migration energies are obtained by means of ab initio calculations; subsequently, self-consistent mean field theory is employed in order to determine the exact Onsager matrix of the alloys. This innovative multiscale approach provides a more complete treatment of the solute-defect interaction than previous multifrequency models. Solute drag is found to be a widespread phenomenon that occurs systematically in ferritic alloys and is enhanced at low temperatures (as for instance RPV operational temperature), as long as an attractive solute-vacancy interaction is present, and that the kinetic modeling of bcc alloys requires the extension of the interaction shell to the second-nearest neighbors. Drag occurs in all alloys except Fe(Cr); the transition from dragging to nondragging regime takes place for the other alloys around (Cu, Mn, Ni) or above (P, Si) the Curie temperature. As far as only the vacancy-mediated solute migration is concerned, Cr depletion at sinks is foreseen by the model, as opposed to the other impurities which are expected to enrich up to no less than 1000 K. The results of this study confirm the current interpretation of the hardening processes in ferritic-martensitic steels under irradiation.

  4. Phase diagram and magnetocaloric effects in Ni{sub 50}Mn{sub 35}(In{sub 1−x}Cr{sub x}){sub 15} and (Mn{sub 1−x}Cr{sub x})NiGe{sub 1.05} alloys

    SciTech Connect

    Quetz, Abdiel Muchharla, Baleeswaraiah; Dubenko, Igor; Talapatra, Saikat; Ali, Naushad; Samanta, Tapas; Stadler, Shane

    2014-05-07

    The magnetocaloric and thermomagnetic properties of Ni{sub 50}Mn{sub 35}(In{sub 1−x}Cr{sub x}){sub 15} and (Mn{sub 1−x}Cr{sub x}) NiGe{sub 1.05} systems for 0 ≤ x ≤ 0.105 and 0 ≤ x ≤ 0.1, respectively, have been studied by x-ray diffraction, differential scanning calorimetry, and magnetization measurements. Partial substitution of Cr for Mn in (Mn{sub 1−x}Cr{sub x})NiGe{sub 1.05} results in a first order magnetostructural transition from a hexagonal paramagnetic to an orthorhombic paramagnetic phase near T{sub M} ∼ 380 K (for x = 0.07). Partial substitution of Cr for In in Ni{sub 50}Mn{sub 35}(In{sub 1−x}Cr{sub x}){sub 15} shifts the magnetostructural transition to a higher temperature (T = T{sub M} ∼ 450 K) for x = 0.1. Large magnetic entropy changes of ΔS = −12 (J/(kgK)) and ΔS = −11 (J/(kgK)), both for a magnetic field change of 5 T, were observed in the vicinity of T{sub M} for (Mn{sub 1−x}Cr{sub x})NiGe{sub 1.05} and Ni{sub 50}Mn{sub 35}(In{sub 1−x}Cr{sub x}){sub 15}, respectively.

  5. Serration Behavior and Pop-in Phenomena in AlxCrCuFeMnNi High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Diao, Haoyan; Xie, Xie; Chen, Shuying; Wang, Gongyao; Yang, Fuqian; Dahmen, Karin; Liaw, Peter

    2015-03-01

    Recently, high-entropy alloys (HEAs), based on achieving a high configuration entropy of mixing among alloying elements, have been developed. Many of these alloys contain expensive elements, such as Co. Substituting these elements for less expensive elements, such as Mn, without compromising the mechanical performance is crucial to make HEAs commercially viable. The AlxCrCuFeMnNi (x = 0.1, 0.3, and 0.8) system is one such alloy that displays encouraging mechanical results in both compression and nanoindentation experiments. Discrete, jerky stress-drop bursts (serrations) are even found at room temperature. The mean-field-interaction model predicts the scaling behavior of the distribution, D(S), of avalanche sizes in the experiments. D(S) follows a power law multiplied by an exponentially-decaying scaling function. The size of the largest observed avalanche depends on experimental parameters, such as aluminum content, strain rate, or temperature. In nanoindentation, a strain burst is manifested by a sudden displacement excursion or `pop-in', following the initial elastic Hertzian contact. The pop-in phenomena becomes more frequent and regular, as the indentation load is greater than 35 mN. A quantitative theory for the serration behavior and pop-in phenomena is a critical issue for understanding the deformation characteristics of HEAs. This work was supported by the Department of Energy No. DE-FE-0008855 and DE-FE-0011194.

  6. Electrical properties of ferromagnetic Ni{sub 2}MnGa and Co{sub 2}CrGa Heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Pushin, V. G.; Belozerova, K. A.

    2013-07-15

    The electrical properties of ferromagnetic Ni{sub 2}MnGa and Co{sub 2}CrGa Heusler alloys are measured in the temperature range 4-900 K. The effect of the energy gap near the Fermi level in the electronic spectrum on the behavior of electrical resistivity and absolute differential thermopower is discussed.

  7. Weathering and precipitation after meteorite impact of Ni, Cr, Fe, Ca and Mn in K-T boundary clays from Stevns Klint

    NASA Astrophysics Data System (ADS)

    Miyano, Yumiko; Yoshiasa, Akira; Tobase, Tsubasa; Isobe, Hiroshi; Hongu, Hidetomo; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

    2016-05-01

    Ni, Cr, Fe, Ca and Mn K-edge XANES and EXAFS spectra were measured on K-T boundary clays from Stevns Klint in Denmark. According to XANES spectra and EXAFS analyses, the local structures of Ni, Cr and Fe in K-T boundary clays is similar to Ni(OH)2, Cr2O3 and FeOOH, respectively. It is assumed that the Ni, Cr and Fe elements in impact related glasses is changing into stable hydrate and oxide by the weathering and diagenesis at the surface of the Earth. Ca in K-T boundary clays maintains the diopside-like structure. Local structure of Ca in K-T clays seems to keep information on the condition at meteorite impact. Mn has a local structure like MnCO3 with divalent state. It is assumed that the origin on low abundant of Mn in the Fe-group element in K-T clays was the consumption by life activity and the diffusion to other parts.

  8. Magnetic anisotropy of Fe1-yXyPt-L10 [X = Cr, Mn, Co, Ni, Cu] bulk alloys

    NASA Astrophysics Data System (ADS)

    Cuadrado, R.; Klemmer, Timothy J.; Chantrell, R. W.

    2014-10-01

    We demonstrate by means of fully relativistic first principles calculations that, by substitution of Fe by Cr, Mn, Co, Ni, or Cu in FePt-L10 bulk alloys, with fixed Pt content, it is possible to tune the magnetocrystalline anisotropy energy by adjusting the content of the non-magnetic species in the material. The changes in the geometry due to the inclusion of each element induces different values of the tetragonality and hence changes in the magnetic anisotropy and in the net magnetic moment. The site resolved magnetic moments of Fe increase with the X content while those of Pt and X are simultaneously reduced. The calculations are in good quantitative agreement with experimental data and demonstrate that models with fixed band structure but varying numbers of electrons per unit cell are insufficient to describe the experimental data for doped FePt-L10 alloys.

  9. Multiferroic approach for Cr,Mn,Fe,Co,Ni,Cu substituted BaTiO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Verma, Kuldeep Chand; Kotnala, R. K.

    2016-05-01

    Multiferroic magnetoelectric (ME) at room temperature is significant for new design nano-scale spintronic devices. We have given a comparative study to report multiferroicity in BaTM0.01Ti0.99O3 [TM = Cr,Mn,Fe,Co,Ni,Cu (1 mol% each) substituted BaTiO3 (BTO)] nanoparticles. The TM ions influenced both nano-size and lattice distortion of Ti–O6 octahedra to the BTO. X ray diffraction study indicates that the dopant TM could influence lattice constants, distortion, tetragonal splitting of diffraction peaks (002/200) as well as peak shifting of diffraction angle in the BTO lattice. This can induce lattice strain which responsible to oxygen defects formation to mediate ferromagnetism. Also, the lattice strain effect could responsible to reduce the depolarization field of ferroelectricity and provide piezoelectric and magnetostrictive strains to enhance ME coupling. The size of BTO nanoparticles is varied in 13–51 nm with TM doping. The room temperature magnetic measurement indicates antiferromagnetic exchange interactions in BTO lattice with TM ions. The zero-field cooling and field cooling magnetic measurement at 500 Oe indicates antiferromagnetic to ferromagnetic transition. It also confirms that the substitution of Cr, Fe and Co into BTO could induce strong antiferromagnetic behavior. However, the substitutions of Mn, Ni and Cu have weak antiferromagnetic character. The temperature dependent dielectric measurements indicates polarization enhancement that influenced with both nano-size as well TM ions and exhibits ferroelectric phase transition with relaxor-like characteristics. Dynamic ME coupling is investigated, and the longitudinal ME voltage coefficient, α ME is equivalent to linear ME coupling coefficient, α (={\\varepsilon }{{o}}{\\varepsilon }{{r}}{α }{{ME}}) is also calculated.

  10. Effect of vanadium and chromium on the microstructural features of V-Cr-Mn-Ni spheroidal carbide cast irons

    NASA Astrophysics Data System (ADS)

    Efremenko, V. G.; Shimizu, K.; Cheiliakh, A. P.; Kozarevskaya, T. V.; Kusumoto, K.; Yamamoto, K.

    2014-11-01

    The objective of this investigation is to study the influence of vanadium (5.0wt%-10.0wt%) and chromium (0-9.0wt%) on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys' microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic (based on M7C3), pearlite, martensite, and austenite. Their combinations and area fraction (AF) ratios are reported to be influenced by the alloys' chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic (γ-Fe + M7C3), preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.

  11. Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr18 FCC solid solution alloy

    SciTech Connect

    Wu, Z.; Bei, H.

    2015-07-01

    Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with a composition of FeNiMnCr18 was successfully developed. This near-equiatomic FeNiMnCr18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.

  12. Microstructural stability and mechanical behavior of FeNiMnCr high entropy alloy under ion irradiation

    DOE PAGESBeta

    Leonard, Keith J.; Bei, Hongbin; Zinkle, Steven J.; Kiran Kumar, N. A. P.; Li, C.

    2016-05-13

    In recent years, high entropy alloys (HEAs) have attracted significant attention due to their excellent mechanical properties and good corrosion resistance, making them potential candidates for high temperature fission and fusion structural applications. However there is very little known about their radiation resistance, particularly at elevated temperatures relevant for energy applications. In the present study, a single phase (face centered cubic) concentrated solid solution alloy of composition 27%Fe-28%Ni-27%Mn-18%Cr was irradiated with 3 or 5.8 MeV Ni ions at temperatures ranging from room temperature to 700 °C and midrange doses from 0.03 to 10 displacements per atom (dpa). Transmission electron microscopymore » (TEM), scanning transmission electron microscopy with energy dispersive x-ray spectrometry (STEM/EDS) and X-ray diffraction (XRD) were used to characterize the radiation defects and microstructural changes. Irradiation at higher temperatures showed evidence of relatively sluggish solute diffusion with limited solute depletion or enrichment at grain boundaries. The main microstructural feature at all temperatures was high-density small dislocation loops. Voids were not observed at any irradiation condition. Nano-indentation tests on specimens irradiated at room temperature showed a rapid increase in hardness ~35% and ~80% higher than the unirradiated value at 0.03 and 0.3 dpa midrange doses, respectively. The irradiation-induced hardening was less pronounced for 500 °C irradiations (<20% increase after 3 dpa). Overall, the examined HEA material exhibits superior radiation resistance compared to conventional single phase Fe-Cr-Ni austenitic alloys such as stainless steels. Furthermore, the present study provides insight on the fundamental irradiation behavior of a single phase HEA material over a broad range of irradiation temperatures.« less

  13. Thermodynamic Stability of Transition-Metal-Substituted LiMn2-x Mx O4 (M=Cr, Fe, Co, and Ni) Spinels.

    PubMed

    Lai, Chenying; Chen, Jiewei; Knight, James C; Manthiram, Arumugam; Navrotsky, Alexandra

    2016-07-01

    The formation enthalpies from binary oxides of LiMn2 O4 , LiMn2-x Crx O4 (x=0.25, 0.5, 0.75 and 1), LiMn2-x Fex O4 (x=0.25 and 0.5), LiMn2-x Cox O4 (x=0.25, 0.5, and 0.75) and LiMn1.75 Ni0.25 O4 at 25 °C were measured by high temperature oxide melt solution calorimetry and were found to be strongly exothermic. Increasing the Cr, Co, and Ni content leads to more thermodynamically stable spinels, but increasing the Fe content does not significantly affect the stability. The formation enthalpies from oxides of the fully substituted spinels, LiMnMO4 (M=Cr, Fe and Co), become more exothermic (implying increasing stability) with decreasing ionic radius of the metal and lattice parameters of the spinel. The trend in enthalpy versus metal content is roughly linear, suggesting a close-to-zero heat of mixing in LiMn2 O4 -LiMnMO4 solid solutions. These data confirm that transition-metal doping is beneficial for stabilizing these potential cathode materials for lithium-ion batteries. PMID:27017448

  14. Kinetic Parameters of Secondary Carbide Precipitation in High-Cr White Iron Alloyed by Mn-Ni-Mo-V Complex

    NASA Astrophysics Data System (ADS)

    Efremenko, V. G.; Chabak, Yu. G.; Brykov, M. N.

    2013-05-01

    This study presents kinetics of precipitation of secondary carbides in 14.55%Cr-Mn-Ni-Mo-V white cast iron during the destabilization heat treatment. The as-cast iron was heat treated at temperatures in the range of 800-1100 °C with soaking up to 6 h. Investigation was carried out by optical and electron microscopy, dilatometric analysis, Ms temperature measurement, and bulk hardness evaluation. TTT-curve of precipitation process of secondary carbides (M7C3, M23C6, M3C2) has been constructed in this study. It was determined that the precipitation occurs at the maximum rate at 950 °C where the process is started after 10 s and completed within 160 min further. The precipitation leads to significant increase of Ms temperature and bulk hardness; large soaking times at destabilization temperatures cause coarsening of secondary carbides and decrease in particles number, followed by decrease in hardness. The results obtained are discussed in terms of solubility of carbon in the austenite and diffusion activation of Cr atoms. The precipitation was found to consist of two stages with activation energies of 196.5 kJ/g-mole at the first stage and 47.1 kJ/g-mole at the second stage.

  15. Electronic and magnetic properties of a new diluted magnetic semiconductor Li(Zn,TM)As (TM:V, Cr, Mn, Fe, Co and Ni)

    NASA Astrophysics Data System (ADS)

    Tao, H. L.; Lin, L.; Zhang, Z. H.; He, M.; Song, B.

    2016-07-01

    First-principles calculations were performed to study electronic structures and magnetic properties of transition metal (TM) doped LiZnAs system. V, Mn, Fe and Co doped LiZnAs preferred anti-ferromagnetic states while no magnetisms were found for Cr and Ni-doped LiZnAs system. In contrast, V/Li, Cr/Li, Mn/Li, Fe/Li and Co/Li codoped LiZnAs preferred ferromagnetic couplings between the TM atoms other than the anti-ferromagnetic states. Thus off-stoichiometry of Li is very essential for the preparation of ferromagnetic LiZnAs materials. For Ni/Li-codoped LiZnAs, anti-ferromagnetic is more stable, which is resulted from the through-bond spin polarization mechanism.

  16. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ≤ 70 kOe. It has been shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  17. Temperature dependencies of the elastic moduli and thermal expansion coefficient of an equiatomic, single-phase CoCrFeMnNi high-entropy alloy

    DOE PAGESBeta

    Laplanche, G.; Gadaud, P.; Horst, O.; Otto, F.; Eggeler, G.; George, E.

    2014-11-15

    The equiatomic CoCrFeMnNi alloy is now regarded as a model face-centered cubic single-phase high-entropy alloy. Consequently, determination of its intrinsic properties such as the temperature dependencies of elastic moduli and thermal expansion coefficient are important to improve understanding of this new class of material. Lastly, these temperature dependencies were measured over a large temperature range (200–1270 K) in this study.

  18. Fractional and group composition of the Mn, Cr, Ni, and Cd compounds in the soils of technogenic landscapes in the impact zone of the Novocherkassk Power Station

    NASA Astrophysics Data System (ADS)

    Minkina, T. M.; Motuzova, G. V.; Mandzhieva, S. S.; Nazarenko, O. G.; Burachevskaya, M. V.; Antonenko, E. M.

    2013-04-01

    The compounds of Cr, Ni, Mn, and Cd in the soils around the Novocherkassk Power Station and the influence of the technogenic and natural factors on their composition were investigated. The data on the fractional and the group composition of these compounds proved to be informative for assessing the ecological state of the soils. The soil components specifying the accumulation and the properties of the heavy metal compounds in the polluted and unpolluted areas were identified.

  19. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

    PubMed Central

    Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

    2015-01-01

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼1 GPa, excellent ductility (∼60–70%) and exceptional fracture toughness (KJIc>200 MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip. PMID:26647978

  20. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

    SciTech Connect

    Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

    2015-12-09

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ~1 GPa, excellent ductility (~60–70%) and exceptional fracture toughness (KJIc>200M Pa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. In conclusion, we further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.

  1. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

    DOE PAGESBeta

    Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

    2015-12-09

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ~1 GPa, excellent ductility (~60–70%) and exceptional fracture toughness (KJIc>200M Pa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening andmore » ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. In conclusion, we further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.« less

  2. Behaviour of Cd, Cr, Mn, Ni, Pb, and Zn in sewage sludge incineration by fluidised bed furnace

    SciTech Connect

    Marani, D.; Braguglia, C.M.; Mininni, G.; Maccioni, F

    2003-07-01

    Cd, Cr, Mn, Ni, Pb, and Zn behaviour during sewage sludge incineration was investigated in seven pilot tests using a circulating fluidised bed furnace. Dewatered sludge at a solids concentration of 15-18% was fed to the furnace either alone (two tests) or spiked with chlorinated organic compounds (five tests). The behaviour of metals in the fluidised bed furnace was studied by comparing metal concentrations in the two main ash streams: ash separated from the cyclone immediately following the fluidised bed furnace, and fly ash recovered in the final bag filter. A metal enrichment factor was defined as the ratio of metal concentration between filter ash and cyclone ash. Only Cd and Pb showed any significant enrichment. Their enrichment factors were mainly affected by chlorine concentration in the feed sludge. To check whether simple equilibrium models may explain and predict metal behaviour, experimental data were compared with percentage of the metal vaporisation in the combustion chamber predicted using a thermodynamic model. Discrepancies between model predictions and experimental results are accounted for by considering that kinetics may be a limiting factor in the formation of metal chloride gaseous species. Due to the very short sludge residence time in the fluidised bed furnace, the gaseous compounds have little chance to evolve completely.

  3. The magnetic and magneto-optical properties of Co, Cr, Mn, and Ni substituted barium ferrite films

    NASA Astrophysics Data System (ADS)

    Carey, R.; Gago-Sandoval, P. A.; Newman, D. M.; Thomas, B. W. J.

    1994-05-01

    Using rapid thermal processing (RTP) we recently demonstrated the production of high quality well ordered barium ferrite films in times much shorter than those required by a conventional annealing process. Influence over the magnetic and structural properties developed in annealed samples was also achieved by variation of the RTP heating profile (R. Carey, P. A. Gago-Sandoval, D. M. Newman, and B. W. J. Thomas, presented at Intermag-93, Stockholm, April 13-16, 1993). It is known that the magneto-optic properties of barium ferrite can be enhanced by selective substitution of some of the Fe by Co2+ and Ti4+ albeit at the expense of reducing the magnetic anisotropy. A multitarget scanning cosputtering process has been used in conjunction with rapid thermal processing to produce a series of barium ferrite films in which Co, Cr, Mn, Ni are selectively introduced to substitute for between 5 and 20 at. % of the Fe. A corresponding percentage of Ti is also added to maintain charge compensation. The magnetic and magneto-optic properties of these films are presented and discussed with reference to their composition and treatment respect to the properties of barium ferrite.

  4. Thermal Behavior of Mechanically Alloyed Powders Used for Producing an Fe-Mn-Si-Cr-Ni Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Pricop, B.; Söyler, U.; Lohan, N. M.; Özkal, B.; Bujoreanu, L. G.; Chicet, D.; Munteanu, C.

    2012-11-01

    In order to produce shape memory rings for constrained-recovery pipe couplings, from Fe-14 Mn-6 Si-9 Cr-5 Ni (mass%) powders, the main technological steps were (i) mechanical alloying, (ii) sintering, (iii) hot rolling, (iv) hot-shape setting, and (v) thermomechanical training. The article generally describes, within its experimental-procedure section, the last four technological steps of this process the primary purpose of which has been to accurately control both chemical composition and the grain size of shape memory rings. Details of the results obtained in the first technological step, on raw powders employed both in an initial commercial state and in a mixture state of commercial and mechanically alloyed (MA) powders, which were subjected to several heating-cooling cycles have been reported and discussed. By means of differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD), the thermal behaviors of the two sample powders have been analyzed. The effects of the heating-cooling cycles, on raw commercial powders and on 50% MA powders, respectively, were argued from the point of view of specific temperatures and heat variations, of elemental diffusion after thermal cycling and of crystallographic parameters, determined by DSC, SEM, and XRD, respectively.

  5. Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi.

    PubMed

    Zhang, ZiJiao; Mao, M M; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X; George, Easo P; Yu, Qian; Ritchie, Robert O

    2015-01-01

    Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼ 1 GPa, excellent ductility (∼ 60-70%) and exceptional fracture toughness (KJIc>200 MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip. PMID:26647978

  6. Effect of Vanadium Nitride Precipitation on Martensitic Transformation and Mechanical Properties of CrMnNi Cast Austenitic Steels

    NASA Astrophysics Data System (ADS)

    Wendler, Marco; Reichel, Benedikt; Eckner, Ralf; Fabrichnaya, Olga; Krüger, Lutz; Weiß, Andreas; Mola, Javad

    2016-01-01

    The microstructural evolution and mechanical properties of two cast Fe-15Cr-6Mn-3Ni-0.5Si-0.2N-0.1C (concentrations in wt pct) steels containing no vanadium and 0.65 wt pct vanadium were investigated under uniaxial tensile loading for room temperature (RT) and 373 K (100 °C). The alloy development was focused on the formation of nanosized vanadium nitride precipitates in the austenite to serve as obstacles to dislocation motion. The austenitic steels exhibited transformation- and twinning-induced plasticity (TRIP/TWIP) effects and the planar glide of dislocations in the austenite. The triggering stress for the RT strain-induced σ γ→ α' formation increased by 190 MPa, and the transformation occurred at higher strain levels due to the presence of VN precipitates. The occurrence of the TWIP effect during tensile testing at 373 K (100 °C) of both steels resulted in engineering strains above 50 pct. The yield strength (YS) of the VN-containing steel was 420 MPa at RT, 52 MPa higher than the vanadium-free alloy. The difference increased to 59 MPa at 373 K (100 °C) with the VN-containing alloy exhibiting a YS of 311 MPa.

  7. Density functional theory study of Mo-doped M@(BN)48 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) clusters

    NASA Astrophysics Data System (ADS)

    Liang, Wenjuan; Jia, Jianfeng; Lv, Jin; Wu, Haishun

    2016-03-01

    The structure and magnetic properties of Mo-doped M@(BN)48 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) clusters were calculated at BPW91/LanL2DZ level. The magnetic nature of the clusters M@(BN)48 significantly changed when doping with Mo atom, except for Co@(BN)48. Only the magnetic moment for the CrMo@(BN)48 cluster was decreased to zero. Thus, M@(BN)48 clusters can be selected as the model system to detect Mo atom by the change of the magnetic moment.

  8. Strong pressure dependences of the magnetization and Curie temperature for CrTe and MnAs with NiAs-type structure

    NASA Astrophysics Data System (ADS)

    Yamada, H.; Terao, K.; Kondo, K.; Goto, T.

    2002-11-01

    To study the strong magneto-volume effects observed in CrTe and MnAs with NiAs-type crystal structure, first-principle band calculations are carried out by a self-consistent linear muffin-tin orbital method within the atomic sphere approximation. The equilibrium volume of the unit cell is obtained as a function of the magnetization M, which gives the volume magnetostriction. The dependence on M of the bulk modulus is also estimated. The coefficients a0 and b0 in the Landau expansion, ΔE(M) = a0 M2 /2 + b 0 M4 /4, are estimated by the fixed-spin-moment method. The calculated results for CrTe and MnAs are compared with those for bcc Fe. It is shown that the values of |a0 | and b0 for CrTe and MnAs are so small that the correction term from the magneto-volume coupling constants becomes significant. This fact gives a strong pressure dependence of the spontaneous magnetization. The pressure dependence of the Curie temperature is also discussed by making use of the magneto-volume coupling constants estimated in the present paper. The large volume magnetostriction observed in CrTe and MnAs is explained by the present calculations.

  9. Influence of transition metals (Cr, Mn, Fe, Co and Ni) on the methane combustion over Pd/Ce-Zr/Al 2O 3 catalyst

    NASA Astrophysics Data System (ADS)

    Yue, Baohua; Zhou, Renxian; Wang, Yuejuan; Zheng, Xiaoming

    2006-06-01

    The effects of transition metals (Cr, Mn, Fe, Co and Ni) on the catalytic properties of Pd/Ce-Zr/Al 2O 3 catalyst for methane combustion have been investigated. The supported Pd catalysts are characterized by BET, XRD, TEM, TPR, TPO and TPSR measurements. Activity tests in methane combustion show that Pd/Ce-Zr-Ni/Al 2O 3 has the highest catalytic activity and thermal stability among all catalysts. The results of TEM show that the addition of Ni to Pd/Ce-Zr/Al 2O 3 increases the dispersion of Pd component and inhibits the site growth. The results of TPO and TPSR show that the addition of Ni inhibits the decomposition of PdO particles and improves the reduction-reoxidation properties of the active PdO species, which increases the catalytic activity and thermal stability of the Pd/Ce-Zr/Al 2O 3 catalyst.

  10. Varied roles of Pb in transition-metal PbMO3 perovskites (M = Ti, V, Cr, Mn, Fe, Ni, Ru)

    NASA Astrophysics Data System (ADS)

    Goodenough, John B.; Zhou, Jianshi

    2015-06-01

    Different structural chemistries resulting from the Pb2+ lone-pair electrons in the PbMO3 perovskites are reviewed. The Pb2+ lone-pair electrons enhance the ferroelectric transition temperature in PbTiO3, stabilize vanadyl formation in PbVO3, and induce a disproportionation reaction of CrIV in PbCrO3. A Pb2+ + NiIV = Pb4+ + NiII reaction in PbNiO3 stabilizes the LiNbO3 structure at ambient pressure, but an A-site Pb4+ in an orthorhombic perovskite PbNiO3 is stabilized at modest pressures at room temperature. In PbMnO3, a ferroelectric displacement due to the lone pair electron effect is minimized by the spin-spin exchange interaction and the strong octahedral site preference of the MnIV/III cation. PbRuO3 is converted under pressure from the defective pyrochlore to the orthorhombic (Pbnm) perovskite structure where Pb-Ru interactions via a common O -2p orbital stabilize at low temperature a metallic Imma phase at ambient pressure. Above Pc ≃ ~32 GPa, a covalent Pb-Ru bond is formed by Pb2+ + RuIV = Pb4+ + RuII electron sharing.

  11. Microstructures and Mechanical Performance of Plasma-Nitrided Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Tang, Wei-Yeh; Chuang, Ming-Hao; Lin, Su-Jien; Yeh, Jien-Wei

    2012-07-01

    This study investigates the effect of plasma nitriding at 798 K (525 °C) on microstructures and the mechanical performance of Al0.3CrFe1.5MnNi0.5 high-entropy alloys (HEAs) obtained using different cast and wrought processing. All the alloys can be well nitride, with a thickness of around 80 μm, and attain a peak hardness level around Hv 1300 near the surface. The main nitride phases are CrN, AlN, and (Mn, Fe)4N. Those of the substrates are bcc, fcc, Al-, and Ni-rich B2 precipitates, and ρ phase. Their relative amounts depend on the prior processing and also change under the heat treatment during nitriding. The formation of ρ phase during nitriding could in-situ harden the substrate to attain the suitable level required for wear applications. This gives the advantage in simplifying the processing for making a wear-resistance component or a mold since austenitizing, quench hardening, and tempering required for steels such as SACM and SKD steels are no longer required and final finishing can be accomplished before nitriding. Nitrided Al0.3CrFe1.5MnNi0.5 samples have much better wear resistance than un-nitrided ones by 49 to 80 times and also exhibit superior adhesive wear resistance to conventional nitrided alloys: nitriding steel SACM-645 (AISI 7140), 316 stainless steel, and hot-mold steel SKD-61 (AISI H13) by 22 to 55 times depending on prior processing. The superiority is due to the fact that the present nitrided alloys possess a much thicker highly hardened layer than the conventional alloys.

  12. Influence of roll and solution treatment processing on shape memory effect of Fe-14Mn-5Si-9Cr-5Ni alloy

    SciTech Connect

    Li, C.L.; Jin, Z.H.

    1998-10-01

    The shape memory effect was studied in an Fe-14Mn-5Si-9Cr-5Ni alloy rerolled at 1123 K after hot rolling at 1423 K, followed by solution treatment at different temperatures. It was found that the alloy exhibits a maximum degree of shape recovery in a bending test and a complete recovery tensile strain of 2.2% in samples that were solution heated at 973 K for 600 s and then quenched in water. The rerolled processing at 1123 K after hot rolling at 1423 K and the microstructure under solution treatment state are important for obtaining a good shape memory effect in the alloy.

  13. A Novel Training-Free Processed Fe-Mn-Si-Cr-Ni Shape Memory Alloy Undergoing δ → γ Phase Transformation

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Wang, Gaixia; Du, Yangyang; Wang, Shanling; Chen, Jie; Wen, Yuhua

    2016-04-01

    We not only suppress the formation of twin boundaries but also introduce a high density of stacking faults by taking advantage of δ → γ phase transformation in a processed Fe-19.38Mn-5.29Si-8.98Cr-4.83Ni shape memory alloy. As a result, its shape memory effect is remarkably improved after heating at 1533 K (1260 °C) (single-phase region of δ ferrite) and air cooling due to δ → γ phase transformation.

  14. A Novel Training-Free Processed Fe-Mn-Si-Cr-Ni Shape Memory Alloy Undergoing δ → γ Phase Transformation

    NASA Astrophysics Data System (ADS)

    Peng, Huabei; Wang, Gaixia; Du, Yangyang; Wang, Shanling; Chen, Jie; Wen, Yuhua

    2016-07-01

    We not only suppress the formation of twin boundaries but also introduce a high density of stacking faults by taking advantage of δ → γ phase transformation in a processed Fe-19.38Mn-5.29Si-8.98Cr-4.83Ni shape memory alloy. As a result, its shape memory effect is remarkably improved after heating at 1533 K (1260 °C) (single-phase region of δ ferrite) and air cooling due to δ → γ phase transformation.

  15. The Mechanical and Corrosion Behaviors of As-cast and Re-melted AlCrCuFeMnNi Multi-Component High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Soare, Vasile; Mitrica, Dumitru; Constantin, Ionut; Popescu, Gabriela; Csaki, Ioana; Tarcolea, Mihai; Carcea, Ioan

    2015-04-01

    A multi-component AlCrCuFeMnNi high-entropy alloy, prepared by vacuum induction melting, was investigated for structural, mechanical, and corrosion characteristics, before and after the re-melting process. Optical microscopy analysis revealed a dendritic solidification behavior. The interdendritic area contains two main phases and occasionally small hard phases. The re-melting process produced a finer dendritic structure, with rounded dendrites and reduced interdendritic hard phases. The SEM-EDAX analysis showed that the dendrite region contains a Widmanstatten type of structure and are composed of Cr-Fe rich phases, whereas the interdendrite region contains Cu and Mn rich phases. XRD analysis revealed two disordered BCC type A2 structures with high Cr and Fe content and an FCC A12 type of structure for the Cu and Mn rich interdendritic phase. The lattice constants, determined by X-ray diffraction, are 2.87 and 2.91 Å for the A2 phases and 3.67 Å for A1 phase. The Vickers micro hardness increased with the homogeneity of the alloy, having a maximum value of 4370 MPa for the re-melted sample. Corrosion tests carried out in 3.5 wt pct sodium chloride aerated solution indicated that the corrosion resistance improved with the re-melting process, being 1.5 to 2 times better than that of 304 stainless steel.

  16. Ternary titanium transition metal bismuthides Ti{sub 4}TBi{sub 2} with T = Cr, Mn, Fe, Co, and Ni

    SciTech Connect

    Richter, C.G.; Jeitschko, W.; Kuennen, B.; Gerdes, M.H.

    1997-11-01

    The title compounds were prepared by reaction of the elemental components and with the exception of the isotypic chromium compound their tetragonal V{sub 4}SiSb{sub 2}-type crystal structures (I4/mcm, Z = 4) were determined and refined from single-crystal X-ray data. Ti{sub 4}CrBi{sub 2}: a = 1051.6(l), c = 506.7(1) pm; Ti{sub 4}Mn Bi{sub 2}: a = 1049.1 (1), c = 497.8 (1) pm, R = 0.031 for 176 structure factors; Ti{sub 4}FeBi{sub 2}: a = 1048.6(1), c = 493.3(1) pm, R = 0.013 (274 F values); Ti{sub 4}CoBi{sub 2}: a = 1050.6(2), c = 488.2(1) pm, R = 0.038 (472 F values); Ti{sub 4}NiBi{sub 2}: a = 1055.4(1), c = 481.4(1) pm, R = 0.020(373 F values), and 14 variable parameters each. The compounds are isotypic with V{sub 4}SiSb{sub 2}, a structure which is isopointal with U{sub 6}Mn and closely related to the structures of W{sub 5}Si{sub 3} and TlTe. All atoms have high coordination numbers. Unusual features of the structure are channels formed solely by the bismuth atoms and linear chains of the heavier transition metal ions with bond distances varying between 253.3 (Cr-Cr) and 240.7 pm (Ni-Ni). The electrical conductivities of Ti{sub 4}TBi{sub 2} (T= Fe,Co, Ni)--determined with a four-probe technique for sintered polycrystalline samples between 4 K and room temperature--indicate metallic behavior. The magnetic susceptibilities of the five compounds were determined with a SQUID magnetometer. Ti{sub 4}CrBi{sub 2}, T{sub i}4FeBi{sub 2}, and Ti{sub 4}NiBi{sub 2} are Pauli paramagnetic. The magnetic susceptibilities of Ti{sub 4}MnBi{sub 2} and Ti{sub 4}CoBi{sub 2} are strongly temperature dependent. The evaluation of these data according to a modified Curie-Weiss law suggests that both compounds contain one unpaired electron per formula unit. A brief discussion of chemical bonding in these compounds leads to the conclusion that considerable Ti-Ti bonding must be present in these bismuthides, in spite of the fact that the shortest Ti-Ti bonds are as long as 299 pm.

  17. The magnetic Curie temperature and exchange coupling between cations in tetragonal spinel oxide Mn{sub 2.5}M{sub 0.5}O{sub 4} (M = Co, Ni, Mn, Cr, and Mg) films

    SciTech Connect

    Kuo, K.; Cheng, C. W.; Chern, G.

    2012-04-01

    Mn{sub 3}O{sub 4} is a Jahn-Taller tetragonal ferrite that has a relatively low Curie temperature (T{sub c}) of {approx}43 K due to weak coupling between the canting spins. In this study, we fabricated a series of 100-nm-thick Mn{sub 2.5}M{sub 0.5}O{sub 4} (M = Co, Ni, Mn, Cr, and Mg) films via oxygen-plasma-assisted molecular beam epitaxy and measured the structural and magnetic properties of these films. These films show single phase quality, and the c-axis lattice parameter of pure Mn{sub 3}O{sub 4} is 0.944 nm, with a c/a ratio {approx}1.16, consistent with the bulk values. The replacement of Mn by M (M = Co, Ni, Cr, and Mg) changes the lattice parameters, and the c/a ratio varies between 1.16 and 1.06 depending upon the cation distribution of the films. The magnetic Curie temperatures of these films also vary in the range of 25-66 K in that Ni and Co enhance the T{sub c} whereas Mg reduces the T{sub c} (Cr shows no effect on the T{sub c}). These changes to the T{sub c} are related to both the element electronic state and the cation distributions in these compounds. As a non-collinear spin configuration can induce electrical polarization, the present study provides a systematic way to enhance the magnetic transition temperature in tetragonal spinel ferrites.

  18. Large adiabatic temperature change in magnetoelastic transition in Ni50Mn35Cr2Sn13 Heusler alloy of granular nanostructure

    NASA Astrophysics Data System (ADS)

    Prakash, H. R.; Sharma, S. K.; Ram, S.; Chatterjee, S.

    2016-05-01

    The Ni-Mn-Sn alloys are a pioneering series of magnetocaloric materials of a huge heat-energy exchanger in the martensite transition. A small additive of nearly 2 at% Cr effectively tunes the valence electron density of 8.090 electrons per atom and a large change in the entropy ΔSM←A = 4.428 J/kg-K (ΔSM→A = 3.695 J/kg-K in the recycle) at the martensite ← austenite phase transition as it is useful for the magnetic refrigeration and other cooling devices. The Cr additive tempers the tetragonality with the aspect ratio c/a = 0.903 of the martensite phase and exhibits an adiabatic temperature change of 10 K. At room temperature, a hysteresis loop exhibits 48.91 emu/g saturation magnetization and 82.1Oe coercivity.

  19. Phase diagram and magnetocaloric effects in Ni{sub 1-x}Cr{sub x}MnGe{sub 1.05}

    SciTech Connect

    Aryal, Anil Quetz, Abdiel; Pandey, Sudip; Eubank, Michael; Dubenko, Igor; Ali, Naushad; Samanta, Tapas; Stadler, Shane

    2015-05-07

    The structural and magnetic properties of the Ni{sub 1−x}Cr{sub x}MnGe{sub 1.05} system (for x = 0, 0.035, 0.070, 0.105) have been studied by x-ray diffraction (XRD), differential scanning calorimetry (DSC), and magnetization measurements. A change in crystal structure from orthorhombic to hexagonal was observed in the XRD data at chromium concentrations of x = 0.035, 0.070, and 0.105. The values of the cell parameters and volume of the unit cell for orthorhombic and hexagonal phase were determined. It was found that the partial substitution of Cr for Ni in Ni{sub 1−x}Cr{sub x}MnGe{sub 1.05} results in a first order magnetostructural transition from antiferromagnetic to ferromagnetic (FM) at T{sub M} = 132 K for x = 0.105. A FM to paramagnetic second order transition has been observed at T{sub C} = 204 K. A magnetic entropy change of |ΔS{sub M}| = 4.5 J/kg K for ΔH = 5 T was observed in the vicinity of T{sub C} and T{sub M} for x = 0.105. The values of the latent heat (L = 2.2 J/g) and corresponding total entropy changes (ΔS{sub T} = 16 J/kg K) have been determined from DSC measurements. A concentration-dependent phase diagram of transition temperatures has been constructed using the magnetic and DSC data.

  20. Phase relationships in the quaternary systems MS-Cr/sub 2/S/sub 3/-In/sub 2/S/sub 3/ (M=Mn,Fe,Co,Ni), miscibility gaps in spinel solid solutons

    SciTech Connect

    Lutz, H.D.; Jung, M.; Wussow, K.

    1986-02-01

    The phase diagrams of the quanternary systems MS-Cr/sub 2/S/sub 3/-In/sub 2/S/sub 3/ wth M=MN,Fe,Ni were studied by x-ray powder photographs of quenched samples. In the quasibinary sections MnIn/sub 2/S/sub 4/-MnCr/sub 2/S/sub 4/ and FeIn/sub 2/S/sub 4/-FeCr/sub 2/S/sub 4/, immiscibility domes exist below 800 and 850/sup 0/C, respectively. At higher temperatures complete series of spinel type solid solutions are formed, which can be quenched to ambient temperature without decomposition. In the NiIn/sub 2/S/sub 4/-NiCr/sub 2/S/sub 4/ section, spinel-type solid solutions are formed in the range from NiIn/sub 2/S/sub 4/ to NiCr/sub 1.7/In/sub 0.3/S/sub 4/ (800/sup 0/C). At lower temperatures decomposition to chromium and indium rich spinel solid solutions occurs. The phase width of Cr/sub 3/S/sub 4/ type NiCr/sub 2/S/sub 4/ is very small. The system NiCr/sub 2/S/sub 4/-In/sub 2/S/sub 3/ is similar to the NiCr/sub 2/S/sub 4/-NiIn/sub 2/S/sub 4/ system, but probably no quasibinary. The fir spectra of the NiCr/sub 2-2X/In/sub 2X/S/sub 4/ (and NiCr/sub 2-2X/Ga/sub 2X/S/sub 4/) solid solutions reveal that the hypothetical spinel NiCr/sub 2/S/sub 4/ is probably metallic. In the sections CoS-In/sub 2/S/sub 3/ and NiS-In/sub 2/S/sub 3/, spinel type solid solutions are formed in the range from In/sub 2/S/sub 3/ to MIN/sub 2/S/sub 4/. The unusually small reaction rates of the solid state equilibration reaction are discussed in terms of the Gibb's enthalpies of forming the spinel mixed crystals and the kinetic retardation of such reactions.

  1. Chemical bonding in the ternary transition metal bismuthides Ti{sub 4}TBi{sub 2} with T=Cr, Mn, Fe, Co, and Ni

    SciTech Connect

    Rytz, R.; Hoffman, R.

    1999-04-05

    The electronic structure and chemical bonding in the ternary transition metal bismuthides Ti{sub 4}TBi{sub 2} (T = Cr, Mn, Fe, Co, and Ni) is investigated by approximate MO calculations of the extended Hueckel tight-binding type. These intermetallic compounds crystallize in a layer structure, repeating sequence T-Ti/Bi-T-Ti/Bi, stacking along c; the late transition metals form linear chains with short T-T bonds. Other important structural elements are face-sharing chains of Ti{sub 4}Bi{sub 2} octahedra and Bi channels. The decrease of the T-T bond lengths from Cr to Ni is more pronounced than expected from the decrease of the metallic radii alone. The analysis of the electronic structure indicates that this behavior arises from the titanium-titanium and titanium-bismuth interlayer interactions. Diminution of the titanium-titanium interlayer distances as one goes from Ti{sub 4}CrBi{sub 2} to Ti{sub 4}NiBi{sub 2} is due to Ti(d)-Ti(d) bonding, which increases with increasing electron filling of the titanium d levels. The titanium-bismuth interactions remain strong along this series, as can also be seen by the constant intralayer/titanium-bismuth distances. A distinguishing feature of the title compounds is the channels formed by bismuth atoms. These channels are filled by Bi-centered, essentially unhybridized 6p orbitals forming a 2D net stacking along c and interacting with each other, stronger in the c direction than perpendicular to it. The possibility of intercalating electrophilic species into these electron-filled voids is also investigated.

  2. Influence of deformation on the structure and the mechanical properties of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy

    NASA Astrophysics Data System (ADS)

    Gorban', B. F.; Nazarenko, V. A.; Danilenko, N. I.; Karpets, M. V.; Krapivka, N. A.; Firstov, S. A.; Makarenko, E. S.

    2014-10-01

    The phase composition, the hardness, and the elasticity modulus of a high-entropy Fe25Cr20Ni20Co10Mn15Al10 alloy have been studied in the as-cast state, after rolling deformation, and after subsequent high-temperature annealing. The alloy consists of the following two phases: solid substitutional solutions with bcc and fcc crystal lattices; in the as-cast state and after annealing the bcc solid solution is ordered according to B2 type (CsCl). The mixture rule is applied for the calculation of the electron density, the atomic radius, and the melting point at grain boundaries and in the grain volume of the alloy after deformation and annealing. The obtained data demonstrate that the alloy is thermally stable.

  3. Thermodynamic laws of the oxygen solubility in liquid metals (Ni, Co, Fe, Mn, Cr) and the formation of oxygen-containing solutions in the alloys based on them

    NASA Astrophysics Data System (ADS)

    Paderin, S. N.; Shil'nikov, E. V.

    2015-12-01

    The solubility of oxygen in liquid Ni, Co, Fe, Mn, and Cr metals (Group IV in the periodic table) has been found for the first time. Linear dependences of the oxygen solubility on the standard Gibbs energy for the oxidation reaction of a liquid metal with gaseous oxygen are found. The revealed function of oxygen solubility is of scientific importance and allows one to develop a theory of oxygen solutions in liquid metals and liquid multicomponent metallic compositions and to calculate the energies of mixing of liquid metals with oxygen from Δ G MO ° for metal oxidation reactions with allowance for pseudoregular-solution model equations. Using the energies of mixing and metal compositions, we calculated the equilibrium oxygen concentrations in a metal molten pool at the end of oxidation stage of melting 08Kh18N10T steel in an arc furnace. This fact indicates practical importance of the found function of the oxygen solubility in metals.

  4. Substitution in ce2tsi3 intermetallic compositions with t = (Cr, Mn, Fe, Co, or Ni) x (Pd or Au) 1-x. Technical report No. 30

    SciTech Connect

    1996-07-10

    Alloys of composition Ce2(3d/T)Si3, with `3d` one of Cr, Mn, Fe, Co or Ni and `T` being Pd or Au, were separated and examined by powder x-ray diffraction. Select single phase compositions were further examined by magnetic susceptibility, by resistivity for the Pd and Co end-members and by specific heat for Ce2CoSi3. For compounds not containing cobalt, effective cerium moments consistent with trivalent cerium were observed. A re-examination of the AlB2 related structure of Ce2CoSi3 by single crystal methods revealed ordering of cobalt within the CoSi3 hexagonal layer. Magnetic susceptibility, resistance and specific heat measurements suggest valence fluctuation behavior of the cerium in Ce2CoSi3. A return to trivalent cerium magnetic behavior occurs on increasing palladium or gold substitution for cobalt.

  5. Functionally Graded High-Alloy CrMnNi TRIP Steel Produced by Local Heat Treatment Using High-Energy Electron Beam

    NASA Astrophysics Data System (ADS)

    Heinze, D.; Buchwalder, A.; Jung, A.; Weidner, A.; Segel, C.; Müller, A.; Zenker, R.; Biermann, H.

    2016-01-01

    Cold-rolled, high-alloy CrMnNi TRIP steel was heat treated by electron beam (EB) treatment. After cold rolling to a deformation degree of 70 pct, the microstructure was mainly martensitic with residual austenite. The aim of the subsequent EB treatment was to improve mechanical properties regarding strength and ductility by grain refinement. The process is influenced by EB-specific parameters, resulting in different temperature-time regimes due to different heating and cooling rates. Grain size gradients over the cross section could not be completely suppressed, but minimized. Investigations included optical microscopy, scanning electron microscopy, hardness measurements, quasi static tensile tests, digital image correlation, and thermography for functionally graded tensile specimens. The local heat treatment was used to set specific tailored properties.

  6. Electrochemically assisted sorption on oxidized multiwalled carbon nanotubes for preconcentration of Cr, Mn, Co, Ni, Cu and Zn from water samples.

    PubMed

    Zawisza, Beata; Sitko, Rafal

    2013-04-21

    The rapid development in nanomaterials and nanotechnologies has provided many new opportunities in the area related to analytical chemistry. In this paper the unique properties of these materials were used in order to preconcentrate heavy metals prior to detection by spectroscopic techniques. A novel, simple and highly reliable method for the preconcentration of trace amounts of chromium, manganese, cobalt, nickel, copper and zinc using electrochemically assisted sorption on oxidized multiwalled carbon nanotubes (MWCNTs) is developed. The proposed method is based on the application of an electric field to support the sorption process on oxidized MWCNTs. The proposed method was used to preconcentrate trace elements from water of pH = 4. After the preconcentration process, oxidized MWCNTs were directly measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer that reduces the number of chemicals required and minimizes sample handling. Besides EDXRF, any spectroscopy technique allowing the measurement of solid samples can be applied. The various parameters including pH of the solution, amounts of oxidized MWCNTs, sample volume and the influence of voltage as well as the time of assisted electric field on the sorption process were investigated for the optimization of the analytical procedure. Under optimized conditions the proposed preconcentration method offers a high recovery of 99% (Cr), 97% (Mn), 94% (Co), 96% (Ni), 92% (Cu) and 93% (Zn) and good precision of sample preparation (RSD) within 3.5-7%. If measurements are performed using the EDXRF spectrometer, the detection limits are 1 ng mL(-1), 5 ng mL(-1), 5 ng mL(-1), 7 ng mL(-1), 1 ng mL(-1), 8 ng mL(-1) for Cr(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II), respectively. PMID:23476917

  7. Interdiffusion in the Ni/TD-NiCr and Cr/TD-NiCr systems

    NASA Technical Reports Server (NTRS)

    Pawar, A. V.; Tenney, D. R.

    1974-01-01

    The diffusion of Ni and Cr into TD-NiCr has been studied over the 900 to 1100 C temperature range. The diffusion couples were prepared by electroplating Cr and Ni on polished TD-NiCr wafers. Concentration profiles produced as a result of isothermal diffusion at 905, 1000, and 1100 C were determined by electron microprobe analysis. The Boltzmann-Matano analysis was used to determine concentration-dependent diffusion coefficients which were found to compare favorably with previously reported values. These data suggest that 2 vol % ThO2 distribution has no appreciable effect on the rates of diffusion in TD-NiCr with a large grain size. This supports the view that an inert dispersoid in an alloy matrix will not in itself lead to enhanced diffusion unless a short-circuit diffusion structure is stabilized.

  8. Composition Dependence of Phase Stability, Deformation Mechanisms, and Mechanical Properties of the CoCrFeMnNi High-Entropy Alloy System

    NASA Astrophysics Data System (ADS)

    Tasan, C. C.; Deng, Y.; Pradeep, K. G.; Yao, M. J.; Springer, H.; Raabe, D.

    2014-10-01

    The proposal of configurational entropy maximization to produce massive solid-solution (SS)-strengthened, single-phase high-entropy alloy (HEA) systems has gained much scientific interest. Although most of this interest focuses on the basic role of configurational entropy in SS formability, setting future research directions also requires the overall property benefits of massive SS strengthening to be carefully investigated. To this end, taking the most promising CoCrFeMnNi HEA system as the starting point, we investigate SS formability, deformation mechanisms, and the achievable mechanical property ranges of different compositions and microstructural states. A comparative assessment of the results with respect to room temperature behavior of binary Fe-Mn alloys reveals only limited benefits of massive SS formation. Nevertheless, the results also clarify that the compositional requirements in this alloy system to stabilize the face-centered cubic (fcc) SS are sufficiently relaxed to allow considering nonequiatomic compositions and exploring improved strength-ductility combinations at reduced alloying costs.

  9. Composition Dependence of Phase Stability, Deformation Mechanisms, and Mechanical Properties of the CoCrFeMnNi High-Entropy Alloy System

    NASA Astrophysics Data System (ADS)

    Tasan, C. C.; Deng, Y.; Pradeep, K. G.; Yao, M. J.; Springer, H.; Raabe, D.

    2014-09-01

    The proposal of configurational entropy maximization to produce massive solid-solution (SS)-strengthened, single-phase high-entropy alloy (HEA) systems has gained much scientific interest. Although most of this interest focuses on the basic role of configurational entropy in SS formability, setting future research directions also requires the overall property benefits of massive SS strengthening to be carefully investigated. To this end, taking the most promising CoCrFeMnNi HEA system as the starting point, we investigate SS formability, deformation mechanisms, and the achievable mechanical property ranges of different compositions and microstructural states. A comparative assessment of the results with respect to room temperature behavior of binary Fe-Mn alloys reveals only limited benefits of massive SS formation. Nevertheless, the results also clarify that the compositional requirements in this alloy system to stabilize the face-centered cubic (fcc) SS are sufficiently relaxed to allow considering nonequiatomic compositions and exploring improved strength-ductility combinations at reduced alloying costs.

  10. Flow stress and microstructural evolution during hot working of alloy 22Cr-13Ni-5Mn-0.3N austenitic stainless steel

    SciTech Connect

    Mataya, M.C.; Perkins, C.A.; Thompson, S.W.; Matlock, D.K.

    1996-05-01

    The stress-strain behavior and the development of microstructure between 850 C and 1,150 C in an austenitic stainless steel, 22Cr-13Ni-5Mn-0.3N, were investigated by uniaxial compression of cylindrical specimens at strain rates between 0.01 and 1 s{sup {minus}1} up to a strain of one. The measured (anisothermal) and corrected (isothermal) flow curves were distinctly different. The flow stress at moderate hot working temperatures, compared to a number of other austenitic alloys, was second only to that of alloy 718. Both static and dynamic recrystallization were observed. Recrystallization was sluggish in comparison to alloy 304L, apparently due to the presence of a fine Cr- and Nb-rich second-phase dispersion, identified as Z phase, which tended to pin the high-angle grain boundaries even at a high temperature of 1,113 C. Recrystallization may also be retarded by preferential restoration through the competitive process of recovery, which is consistent with the relatively high stacking-fault energy for this alloy. It is concluded that this alloy must be hot worked at temperatures higher than usual for austenitic stainless steels in order to minimize flow stress and refine grain size.

  11. Electron capture of strongly screening nuclides 56Fe, 56Co, 56Ni, 56Mn,56Cr and 56V in pre-supernovae

    NASA Astrophysics Data System (ADS)

    Liu, Jing-Jing

    2013-08-01

    According to the shell-model Monte Carlo method, based on the random-phase approximation and linear response theory, we carried out an estimation of electron capture (EC) of the strongly screening nuclides 56Fe, 56Co, 56Ni, 56Mn,56Cr and 56V during strong electron screening (SES) in pre-supernovae. The EC rates are decreased greatly and may even exceed 21.5 per cent in the case of SES. We also compare our results with those calculated by the method of Aufderheide in the case of SES. Our results agree reasonably well with those of Aufderheide in higher density and temperature surroundings (e.g. ρ7 > 60, T9 = 15.40) and the maximum error is ˜0.5 per cent. However, the maximum error is ˜13.0 per cent in lower density surroundings (e.g. 56Cr at ρ7 = 10, T9 = 15.40, Ye = 0.41). We also compared our results for SES with those of Fuller, Fowler & Newman and Nabi, which apply to a case without SES. The comparisons show that our results are lower than those of Fuller, Fowler & Newman by more than one order of magnitude and about 7.23 per cent lower than those of Nabi.

  12. First-principles study of the inversion thermodynamics and electronic structure of Fe M2X4 (thio)spinels (M =Cr , Mn, Co, Ni; X =O , S)

    NASA Astrophysics Data System (ADS)

    Santos-Carballal, David; Roldan, Alberto; Grau-Crespo, Ricardo; de Leeuw, Nora H.

    2015-05-01

    Fe M2X4 spinels, with the magnetite structure, where M is a transition metal and X is oxygen or sulfur, are candidate materials for spin filters, one of the key devices in spintronics. We present here a computational study of the inversion thermodynamics and the electronic structure of these (thio)spinels for M =Cr ,Mn ,Co ,Ni , using calculations based on the density functional theory with on-site Hubbard corrections (DFT +U ). The analysis of the configurational free energies shows that different behavior is expected for the equilibrium cation distributions in these structures: FeC r2X4 and FeM n2S4 are fully normal, FeN i2X4 and FeC o2S4 are intermediate, and FeC o2O4 and FeM n2O4 are fully inverted. We have analyzed the role played by the size of the ions and by the crystal field stabilization effects in determining the equilibrium inversion degree. We also discuss how the electronic and magnetic structure of these spinels is modified by the degree of inversion, assuming that this could be varied from the equilibrium value. We have obtained electronic densities of states for the completely normal and completely inverse cation distribution of each compound. FeC r2X4 ,FeM n2X4 ,FeC o2O4 , and FeN i2O4 are half-metals in the ferrimagnetic state when Fe is in tetrahedral positions. When M is filling the tetrahedral positions, the Cr-containing compounds and FeM n2O4 are half-metallic systems, while the Co and Ni spinels are insulators. The Co and Ni sulfide counterparts are metallic for any inversion degree together with the inverse FeM n2S4 . Our calculations suggest that the spin filtering properties of the Fe M2X4 (thio)spinels could be modified via the control of the cation distribution through variations in the synthesis conditions.

  13. Dependence of steady-state radiation swelling rate of l 0.1C-16Cr-15Ni-2Mo-2Mn-Ti-Si austenitic steel on dpa rate and irradiation temperature

    NASA Astrophysics Data System (ADS)

    Kozlov, А. V.; Portnykh, I. А.

    2009-04-01

    A large number of swelling measurement data on the 0.1C-16Cr-15Ni-2Mo-2Mn-Ti-Si austenitic steel used as a fuel cladding at temperatures 640-870 К in the BN-600 fast reactor were analyzed. It was found that within irradiation temperatures 690-830 К a steady-state swelling dose rate was from 0.45%/dpa to 1.1%/dpa. By the statistical model of point defect migration for the 0.1C-16Cr-15Ni-2Mo-2Mn-Ti-S steel the dependence of the steady-state swelling rate on the irradiation temperature and displacement rate was calculated. The calculation data were consistent with the experimental data.

  14. Increasing the ordering temperatures in oxalate-based 3D chiral magnets: the series [Ir(ppy)2(bpy)][M(II)M(III)(ox)3] x 0.5 H2O (M(II)M(III) = MnCr, FeCr, CoCr, NiCr, ZnCr, MnFe, FeFe); bpy = 2,2'-bipyridine; ppy = 2-phenylpyridine; ox = oxalate dianion).

    PubMed

    Clemente-León, Miguel; Coronado, Eugenio; Gómez-García, Carlos J; Soriano-Portillo, Alejandra

    2006-07-10

    The synthesis, structure, and physical properties of a novel series of oxalate-based bimetallic magnets obtained by using the Ir(ppy)2(bpy)]+ cation as a template of the bimetallic [M(II)M(III)(ox)3]- network are reported. The compounds can be formulated as [Ir(ppy)2(bpy)][M(II)Cr(III)(ox)3] x 0.5 H2O (M(II) = Ni, Mn, Co, Fe, and Zn) and [Ir(ppy)2(bpy)]-[M(II)Fe(III)(ox)3] x 0.5 H2O (M(II) = Fe, Mn) and crystallize in the chiral cubic space group P4(1)32 or P4(3)32. They show the well-known 3D chiral structure formed by M(II) and M(III) ions connected through oxalate anions with [Ir(ppy)2(bpy)]+ cations and water molecules in the holes left by the oxalate network. The M(II)Cr(III) compounds behave as soft ferromagnets with ordering temperatures up to 13 K, while the Mn(II)Fe(III) and Fe(II)Fe(III) compounds behave as a weak ferromagnet and a ferrimagnet, respectively, with ordering temperatures of 31 and 28 K. These values represent the highest ordering temperatures so far reported in the family of 3D chiral magnets based on bimetallic oxalate complexes. PMID:16813431

  15. Studies on some salicylaldehyde Schiff base derivatives and their complexes with Cr(III), Mn(II), Fe(III), Ni(II) and Cu(II).

    PubMed

    Abdel-Latif, S A; Hassib, H B; Issa, Y M

    2007-07-01

    The formation constants of some transition metal ions Cr(III), Mn(II), Fe(III), Ni(II) and Cu(II) binary complexes containing Schiff bases resulting from condensation of salicylaldehyde with aniline (I), 2-aminopyridine (II), 4-aminopyridine (III) and 2-aminopyrimidine (IV) were determined pH-metrically in ethanolic medium (80%, v/v). The formation constants were determined for all binary complexes. The important infrared (IR) spectral bands corresponding to the active groups in the four ligands and the solid complexes under investigation were studied. The solid complexes have been synthesized and studied by thermogravimetric analysis. The thermal dehydration and decomposition of these complexes were studied kinetically using the integral method applying the Coats-Redfern equation. It was found that the thermal decomposition of the complexes follow second order kinetics. The thermodynamic parameters of the decomposition are also reported. The electronic absorption spectra of the investigated ligands were carried out to determine the pK(a) values spectrophotometrically. PMID:17084104

  16. Studies on some salicylaldehyde Schiff base derivatives and their complexes with Cr(III), Mn(II), Fe(III), Ni(II) and Cu(II)

    NASA Astrophysics Data System (ADS)

    Abdel-Latif, S. A.; Hassib, H. B.; Issa, Y. M.

    2007-07-01

    The formation constants of some transition metal ions Cr(III), Mn(II), Fe(III), Ni(II) and Cu(II) binary complexes containing Schiff bases resulting from condensation of salicylaldehyde with aniline (I), 2-aminopyridine (II), 4-aminopyridine (III) and 2-aminopyrimidine (IV) were determined pH-metrically in ethanolic medium (80%, v/v). The formation constants were determined for all binary complexes. The important infrared (IR) spectral bands corresponding to the active groups in the four ligands and the solid complexes under investigation were studied. The solid complexes have been synthesized and studied by thermogravimetric analysis. The thermal dehydration and decomposition of these complexes were studied kinetically using the integral method applying the Coats-Redfern equation. It was found that the thermal decomposition of the complexes follow second order kinetics. The thermodynamic parameters of the decomposition are also reported. The electronic absorption spectra of the investigated ligands were carried out to determine the p Ka values spectrophotometrically.

  17. Microstructure of CrMnNi Cast Steel After Explosive-Driven Flyer-Plate Impact at Room Temperature and Below

    NASA Astrophysics Data System (ADS)

    Eckner, R.; Reichel, B.; Savinykh, A. S.; Krüger, L.; Razorenov, S. V.; Garkushin, G. V.

    2016-01-01

    A low-carbon metastable austenitic CrMnNi cast steel was investigated under shock conditions in a flyer-plate impact test. The samples were impacted by aluminum flyer-plates with impact velocities of 620 ± 30 m/s. Depending on deformation temperature and strain rate, the material exhibited different deformation mechanisms (dislocation glide, martensitic transformation, and mechanical twinning), which determined the microstructural evolution and mechanical behavior. Flyer-plate impact tests were carried out at 213 K and 293 K (-60 °C and +20 °C). A soft recovered sample revealed microstructural changes directly after impact. The subsequent microstructural investigations via light-optical microscopy and scanning electron microscopy revealed that transformation-induced plasticity (TRIP effect) was the primary deformation mechanism. Moreover, it was possible to quantify the martensite volume fraction by different methods and to identify the hcp ɛ-martensite phase as an intermediate transformation stage. A decrease in temperature also increased the driving force for the martensitic transformation.

  18. Succulent species differ substantially in their tolerance and phytoextraction potential when grown in the presence of Cd, Cr, Cu, Mn, Ni, Pb, and Zn.

    PubMed

    Zhang, Chengjun; Sale, Peter W G; Clark, Gary J; Liu, Wuxing; Doronila, Augustine I; Kolev, Spas D; Tang, Caixian

    2015-12-01

    Plants for the phytoextraction of heavy metals should have the ability to accumulate high concentrations of such metals and exhibit multiple tolerance traits to cope with adverse conditions such as coexistence of multiple heavy metals, high salinity, and drought which are the characteristics of many contaminated soils. This study compared 14 succulent species for their phytoextraction potential of Cd, Cr, Cu, Mn, Ni, Pb, and Zn. There were species variations in metal tolerance and accumulation. Among the 14 succulent species, an Australian native halophyte Carpobrotus rossii exhibited the highest relative growth rate (20.6-26.6 mg plant(-1) day(-1)) and highest tolerance index (78-93%), whilst Sedum "Autumn Joy" had the lowest relative growth rate (8.3-13.6 mg plant(-1) day(-1)), and Crassula multicava showed the lowest tolerance indices (<50%). Carpobrotus rossii and Crassula helmsii showed higher potential for phytoextraction of these heavy metals than other species. These findings suggest that Carpobrotus rossii is a promising candidate for phytoextraction of multiple heavy metals, and the aquatic or semiterrestrial Crassula helmsii is suitable for phytoextraction of Cd and Zn from polluted waters or wetlands. PMID:26201657

  19. Correlation of acoustic emission generated during uniform biaxial loading to microstructural sources in 7075-T651 aluminum and 21Cr-6Ni-9Mn stainless steel. Final report

    SciTech Connect

    Leon, E.; Mukherjee, A.K.

    1981-12-01

    This paper reports on the effect on acoustic emission (AE) of uniform biaxial loading of a thin-walled tube designed by Hamstad, Patterson and Mukherjee. The AE generated during biaxial loading of 7075-T651 aluminum and 21Cr-6Ni-9Mn stainless steel had several anomalous features relative to tensile generated AE. The biaxial AE data was of a much higher level and peaked at a lower strain than the uniaxial AE response. A particle cracking model was proposed in which inclusions with the largest projected surface area perpendicular to the principal axis of applied loading will crack before smaller inclusions, and the resulting energy released per AE will be proportional to the crack surface area. The inclusion contents were studied with respect to size, shape, density, hardness, and fracture/decohesion behavior. The inclusions in both 7075-T651 and 21-6-9 display the preferred cracking orientation predicted in the Hamstad, et al. model and are shown to be associated with the generated AE. However, other factors appear to contribute to the total AE responses. There is evidence that for 7075-T651 subjected to biaxial loading, a grain boundary-related mechanism becomes a significant source of AE in the latter stages of strain hardening. Also, for both materials, the complex applied load during biaxial loading appears to amplify the level of AE.

  20. In quest of cathode materials for Ca ion batteries: the CaMO3 perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni).

    PubMed

    Arroyo-de Dompablo, M E; Krich, C; Nava-Avendaño, J; Palacín, M R; Bardé, F

    2016-07-20

    Basic electrochemical characteristics of CaMO3 perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni) as cathode materials for Ca ion batteries are investigated using first principles calculations at the Density Functional Theory level (DFT). Calculations have been performed within the Generalized Gradient Approximation (GGA) and GGA+U methodologies, and considering cubic and orthorhombic perovskite structures for CaxMO3 (x = 0, 0.25, 0.5, 0.75 and 1). The analysis of the calculated voltage-composition profile and volume variations identifies CaMoO3 as the most promising perovskite compound. It combines good electronic conductivity, moderate crystal structure modifications, and activity in the 2-3 V region with several intermediate CaxMoO3 phases. However, we found too large barriers for Ca diffusion (around 2 eV) which are inherent to the perovskite structure. The CaMoO3 perovskite was synthesized, characterized and electrochemically tested, and results confirmed the predicted trends. PMID:27398629

  1. Energy of vacancy migration in 0.06C-16Cr-15Ni-2Mo-2Mn-Ti-Si-V-B and 0.07C-16Cr-19Ni-2Mo-2Mn-Ti-Si-V-P-B cladding steels

    NASA Astrophysics Data System (ADS)

    Kozlov, A. V.; Portnykh, I. A.; Tselishchev, A. V.; Shilo, O. B.; Asiptsov, O. I.

    2014-05-01

    Samples of 0.06C-16Cr-15Ni-2Mo-2Mn-Ti-Si-V-B and 0.07C-16Cr-19Ni-2Mo-2Mn-Ti-Si-V-P-B steels (ChS68 and EK164 steels, respectively) in the form of fuel element cladding tubes from a BN-600 reactor have been subjected to neutron irradiation in an IVV-2M research reactor to damage doses of 0.0015, 0.0050, and 0.0100 dpa at a temperature of 30°C. Based on a comparison of the results of dilatometric measurements of the irradiated samples and the samples in the initial state, the energies of vacancy migration in the steels are calculated. It is found that the energy of vacancy migration is 1.08 ± 0.02 eV in the ChS68 steel and 0.98 ± 0.02 eV in the EK164 steel. Using these values, the steady-state vacancy concentrations during irradiation of these steels in the BN-600 reactor are calculated. It is shown that the steady-state vacancy concentration in the EK164 fuel cladding portions irradiated in the lower half of the core is significantly lower than that in the ChS68 cladding. This is a cause of the higher resistance of the former steel to radiation-induced swelling as compared to that of the ChS68 steel upon irradiation in fast neutron breeders.

  2. Apatite/Melt Partitioning Experiments Reveal Redox Sensitivity to Cr, V, Mn, Ni, Eu, W, Th, and U

    NASA Technical Reports Server (NTRS)

    Righter, K.; Yang, S.; Humayun, M.

    2016-01-01

    Apatite is a common mineral in terrestrial, planetary, and asteroidal materials. It is commonly used for geochronology (U-Pb), sensing volatiles (H, F, Cl, S), and can concentrate rare earth elements (REE) during magmatic fractionation and in general. Some recent studies have shown that some kinds of phosphate may fractionate Hf and W and that Mn may be redox sensitive. Experimental studies have focused on REE and other lithophile elements and at simplified or not specified oxygen fugacities. There is a dearth of partitioning data for chalcophile, siderophile and other elements between apatite and melt. Here we carry out several experiments at variable fO2 to study the partitioning of a broad range of trace elements. We compare to existing data and then focus on several elements that exhibit redox dependent partitioning behavior.

  3. Electron-impact excitation of H-like Cr, Mn, Fe, Co, and Ni for applications in modeling X-ray astrophysical sources

    NASA Astrophysics Data System (ADS)

    Malespin, C.; Ballance, C. P.; Pindzola, M. S.; Witthoeft, M. C.; Kallman, T. R.; Loch, S. D.

    2011-02-01

    Context. Accurate atomic data for the less abundance Fe-peak elements are required for use in X-ray astrophysical studies. Aims: We calculate high quality electron-impact excitation collision strengths and effective collision strengths for hydrogenic Cr, Mn, Fe, Co, and Ni. Methods: We use the Dirac R-matrix method, the intermediate coupling frame transformation R-matrix method, the semi-relativistic distorted-wave method and the fully-relativistic distorted-wave method to calculate collision strengths for each of the ions. The ADAS collisional-radiative codes are used to produce photon emissivity coefficients for each ion. Results: Results are presented for atomic energy levels, spontaneous emission coefficients, electron-impact excitation collision strengths and associated effective collision strengths for each of the five species under consideration. We find relativistic effects can contribute an approximate 10% increase to the background cross section in relation to semi-relativistic collision calculations. We also confirm that radiation damping plays a prominent role for certain near threshold resonances. In order check the integration of our results within collisional-radiative modeling codes, we have used the ADAS package for some preliminary modeling of photon emissivities. The atomic data shall be made available online through the OPEN-ADAS site and the CFADC database Final datasets for each ion are only available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A115

  4. The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy

    SciTech Connect

    Otto, Frederik; Dlouhy, A.; Somsen, Ch.; Bei, Hongbin; Eggeler, G.; George, Easo P

    2013-01-01

    An equiatomic CoCrFeMnNi high-entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was produced by arc melting and drop casting. The drop-cast ingots were homogenized, cold rolled, and recrystallized to obtain single-phase microstructures with three different grain sizes in the range 4~160 m. Quasi-static tensile tests were then performed at temperatures between 77 and 1073 K. Yield strength, ultimate tensile strength and ductility all increased with decreasing temperature. During the initial stages of plasticity (up to ~2% strain), deformation occurs by planar dislocation glide on the normal FCC slip system {111} 110 at all temperatures and grain sizes investigated. Undissociated 1/2 110 dislocations were observed, as were numerous stacking faults, which imply the dissociation of several of these dislocations into 1/6 112 Shockley partials. At later stages ( 20% strain), nanoscale deformation twins were observed after interrupted tests at 77 K, but not in specimens tested at room temperature where plasticity occurred exclusively by dislocations which organized into cells. Deformation twinning, by continually decreasing the mean free path of dislocations during tensile testing, produces a high degree of work hardening and a significant increase in the ultimate tensile strength. This increased work hardening prevents the early onset of necking instability and is a reason for the enhanced ductility observed at 77 K. A second way in which twinning can contribute to ductility is by providing an additional deformation mode to accommodate plasticity. However, it cannot explain the increase in yield strength with decreasing temperature in our high-entropy alloy since twinning was not observed in the early stages of plastic deformation. Since strong temperature dependencies of yield strength are also seen in binary FCC solid solution alloys, it may be an inherent solute effect, which needs further study.

  5. Ab initio GGA+U study of oxygen evolution and oxygen reduction electrocatalysis on the (001) surfaces of lanthanum transition metal perovskites LaBO₃ (B = Cr, Mn, Fe, Co and Ni).

    PubMed

    Lee, Yueh-Lin; Gadre, Milind J; Shao-Horn, Yang; Morgan, Dane

    2015-09-01

    In this work, we performed density functional theory (DFT) calculations with inclusion of Hubbard U corrections for the transition metal d-electrons, to investigate stability and electrocatalytic activities of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) for the ABO3 (A = La; B = Cr, Mn, Fe, Co, and Ni) (001) surfaces. We showed surface binding energies of relevant ORR/OER species are coupled strongly to surface polarity and local oxidation states, giving large (∼1 eV scale per adsorbate) differences in binding between (001) AO and BO2 surfaces, where the more oxidized BO2 bare surfaces in general exhibit weak coverage dependence, while the more reduced AO bare surfaces of the LaCrO3, LaMnO3, and LaFeO3 perovskites with lower d-electron filling show strong/moderate coverage dependences. We then predicted that surface coverage can play a key role in determining surface stability, and when coverage effects are included the AO and BO2(001) surfaces have either similar stability or the AO surface is more stable, as found for 1 monolayer HO* covered AO surfaces of LaCrO3 and LaFeO3 under ORR conditions and 1 monolayer O* covered LaNiO3 AO surface under OER conditions. For the (001) AO surfaces with strong coverage dependent surface adsorption, we predicted a decrease in ORR overpotential of 1-2 V with proper treatment of coverage effects as compared to those of the bare surface simulations. Our results indicated that the GGA+U method and proper treatment of coverage effects more accurately predict ORR and OER overpotentials relative to experimental values as compared to the GGA method and bare surfaces. The overall ORR activity trends vs. the LaBO3 series were predicted to be Co > MnNi > Fe > Cr. PMID:26227442

  6. Thermal Stability of Ni-Mn Electrodeposits

    SciTech Connect

    Talin, A. A.; Marquis, E. A.; Goods, S. H.; Kelly, J. J.; Miller, Michael K

    2006-01-01

    The effect of Mn additions on the structural stability of electrodeposited Ni is investigated by comparing the microstructure evolution of Ni and Ni-Mn specimens with similar crystallographic initial textures. As deposited, Ni-Mn electrodeposits have a smaller crystallite size and substantially higher yield strength than Ni deposits, in agreement with the Hall-Petch relationship. Moreover, dilute Ni-Mn electrodeposits exhibit a thermal stability that significantly exceeds that of pure Ni. Indeed, Ni-Mn retains its texture, fine-grain microstructure, and strength above 500 C (for 1 h anneal), and does not recrystallize up to 800 C. In contrast, pure Ni with larger average grain size and similar preferred orientation shows abnormal grain growth at 300 C and recrystallization at 600 C. This study suggests two distinct temperature regimes. Below 600 C, grain boundary segregation appears as a plausible mechanism for the thermal stability of Ni-Mn electrodeposits, whereas grain boundary pinning by precipitation contributes to the improved microstructural stability of Ni-Mn above 600 C.

  7. Electrochemical and corrosion properties of YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Cu, Co, Mn) hybride-forming alloys

    SciTech Connect

    Korobov, I.I.; Vasina, S.Ya.; Petrii, O.A.

    1995-06-01

    Hydrogen sorption by electrode materials based on YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Co, Cu, Mn) intermetallic compounds (IMC) with Cu and PTFE binders is studied in 1 M NaOH solution. The obtained reversible electrochemical capacities correspond to YNi{sub 2.5}M{sub 0.5}H{sub 1.3-1.7} hybrides which are stable at room temperature and atmospheric pressure. The application of Cu binder allows one to more completely use the material sorption capacity and promotes both extraction and sorption of hydrogen by IMC.

  8. Investigation on the Interactions of NiCR and NiCR-2H with DNA

    PubMed Central

    Chitranshi, Priyanka; Chen, Chang-Nan; Jones, Patrick R.; Faridi, Jesika S.; Xue, Liang

    2010-01-01

    We report here a biophysical and biochemical approach to determine the differences in interactions of NiCR and NiCR-2H with DNA. Our goal is to determine whether such interactions are responsible for the recently observed differences in their cytotoxicity toward MCF-7 cancer cells. Viscosity measurement and fluorescence displacement titration indicated that both NiCR and NiCR-2H bind weakly to duplex DNA in the grooves. The coordination of NiCR-2H with the N-7 of 2′-deoxyguanosine 5′-monophosphate (5′-dGMP) is stronger than that of NiCR as determined by 1H NMR. NiCR-2H, like NiCR, can selectively oxidize guanines present in distinctive DNA structures (e.g., bulges), and notably, NiCR-2H oxidizes guanines more efficiently than NiCR. In addition, UV and 1H NMR studies revealed that NiCR is oxidized into NiCR-2H in the presence of KHSO5 at low molar ratios with respect to NiCR (≤4). PMID:20671951

  9. Atmospheric metal pollution (Cr, Cu, Fe, Mn, Ni, Pb and Zn) in Oporto city derived from results for low-volume aerosol samplers and for the moss Sphagnum auriculatum bioindicator.

    PubMed

    Vasconcelos, M T; Tavares, H M

    1998-03-01

    A low-volume aerosol sampler with filters and bags of Sphagnum auriculatum were exposed, in parallel, to the atmosphere of Oporto city for approx. 2 months in 1994, during a dry weather period. The levels of Cr, Cu, Fe, Mn, Ni, Pb and Zn in the moss (weekly samples) and in the filters (daily samples) were determined by atomic absorption spectrophotometry and the results were compared. For all the heavy metals, the rate of metal uptake by moss was significantly correlated with the metal concentration in atmospheric aerosols. The results indicated that moss bags of S. auriculatum can provide a quantitative estimation of the concentration of different heavy metals in urban atmospheres, when specific calibration by mechanic monitoring, at the same sampling point, is performed during a first stage of biomonitoring. The mean aerosol metal concentrations found in the Oporto atmosphere were similar to those observed in other urban atmospheres in different countries. The relative order of the mean metal concentrations was Fe (1.8 micrograms/m3) > Zn > Pb > Cu > Cr > Mn > Ni (20 ng/m3). The aerosol Pb levels were monitored at different sampling points over various periods of time between 1991 and 1997. The mean Pb levels were < or = 0.5 microgram/m3 and approximately constant at each sample point up to January 1996. After that date it decreased by approx. 50%, in consequence of the reduction of the Pb concentration in leaded gasoline. PMID:9525044

  10. Combination of Different In Situ Characterization Techniques and Scanning Electron Microscopy Investigations for a Comprehensive Description of the Tensile Deformation Behavior of a CrMnNi TRIP/TWIP Steel

    NASA Astrophysics Data System (ADS)

    Weidner, Anja; Biermann, Horst

    2015-08-01

    The class of low-carbon, high-alloy CrMnNi steels exhibits outstanding mechanical properties with respect to high strength and ductility due to either transformation-induced plasticity (TRIP) or twinning-induced plasticity (TWIP) effect depending on chemical composition and deformation temperature. However, the ongoing deformation mechanisms like the formation of stacking faults, martensitic phase transformation or deformation-induced twinning are overlapping and the kinetics of the microstructure evolution are quite complex. Therefore, in addition to macroscopic deformation tests and microstructural investigations by scanning electron microscopy, a combination of several in situ characterization techniques with either high lateral and/or temporal resolution as well as providing integral volume information were chosen in order to give a thoroughly and comprehensive description of the deformation behavior of CrMnNi TRIP/TWIP steels. In addition, the complementary in situ techniques like in situ nanoindentation, micro-digital image correlation, and acoustic emission measurements provide excellent possibility for description of materials behavior on a multiscale level from the submicrometer scale up to the macroscopic range. The results obtained by the complementary techniques can support the future modeling of the deformation behavior of TRIP/TWIP steels dependent on chemical composition, temperature, grain size and grain orientation.

  11. Electronic structure and bonding of the 3d transition metal borides, MB, M =Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu through all electron ab initio calculations

    NASA Astrophysics Data System (ADS)

    Tzeli, Demeter; Mavridis, Aristides

    2008-01-01

    The electronic structure and bonding of the ground and some low-lying states of all first row transition metal borides (MB), ScB, TiB, VB, CrB, MnB, FeB, CoB, NiB, and CuB have been studied by multireference configuration interaction (MRCI) methods employing a correlation consistent basis set of quintuple cardinality (5Z). It should be stressed that for all the above nine molecules, experimental results are essentially absent, whereas with the exception of ScB and CuB the remaining seven species are studied theoretically for the first time. We have constructed full potential energy curves at the MRCI/5Z level for a total of 27 low-lying states, subsequently used to extract binding energies, spectroscopic parameters, and bonding schemes. In addition, some 20 or more states for every MB species have been examined at the MRCI/4Z level of theory. The ground state symmetries and corresponding binding energies (in kcal/mol) are Σ-5(ScB), 76; Δ6(TiB), 65; Σ+7(VB), 55; Σ+6(CrB), 31; Π5(MnB), 20; Σ-4(FeB), 54; Δ3(CoB), 66; Σ+2(NiB), 79; and Σ+1(CuB), 49.

  12. An improved diffusion welding technique for TD-NiCr

    NASA Technical Reports Server (NTRS)

    Holko, K. H.

    1973-01-01

    An improved diffusion welding technique has been developed for TD-NiCr sheet. In the most preferred form, the improved technique consists of diffusion welding 320-grit sanded plus chemically polished surfaces of unrecrystallized TD-NiCr at 760 C under 140 MN/m2 pressure for 1hr followed by postheating at 1180 C for 2hr. Compared to previous work, this improved technique has the advantages of shorter welding time, lower welding temperature, lower welding pressure, and a simpler and more reproducible surface preparation procedure. Weldments were made that had parent-metal creep-rupture shear strength at 1100 C.

  13. Bis(azulene) "submarine" metal dimer sandwich compounds (C10H8)2M2(M = Ti, V, Cr, Mn, Fe, Co, Ni): Parallel and opposed orientations.

    PubMed

    Wang, Hongyan; Wang, Hui; King, R Bruce; Schaefer, Henry F

    2016-01-15

    The opposed and parallel structures for the binuclear bis(azulene) "submarine" sandwiches (C10H8)2M2 (M = Ti, V, Cr, Mn, Fe, Co, Ni) have been optimized using density functional theory. The lowest energy (C10H8)2 M2 structures of the early transition metals Ti, V, Cr, and Mn have the azulene units functioning as bis(pentahapto) ligands to each metal atom similar to the azulene ligand in the long-known molybdenum carbonyl complex (η(5),η(5)-C10H8 )Mo2 (CO)6 . The metal-metal bonds in these early transition metal structures have distances and Wiberg bond indices consistent with the formal bond orders required to give each metal atom an 18-electron configuration for the singlet structures and a 17-electron configuration for the triplet structures. For the later transition metals Fe, Co, and Ni, the lowest energy (C10H8)2 M2 structures contain pentahapto-trihapto azulene ligands with an uncomplexed C=C double bond, similar to that in the long-known iron carbonyl complex (η(5),η(3)-C10H8)Fe2 (CO)5 . The parallel (η(5),η(3)-C10H8 )2M2 (M = Fe, Co, Ni) structures contain metallocene subunits with their metal atoms at long nonbonding distances of 3.5-3.9 Å from the other metal atom, which is located between the azulene C7 rings. Higher energy opposed (C10H8)2 Fe2 structures contain an unprecedented distorted η(6) ,η(4) -azulene ligand using six carbon atoms for bonding to one iron atom as a hexahapto fulvene ligand and the remaining four carbon atoms for bonding to the other iron atom as a tetrahapto diene ligand. PMID:26213099

  14. Metal distribution and disorder in the crystal structure of [NH2Et2][Cr7MF8((t)BuCO2)16] wheel molecules for M = Mn, Fe, Co, Ni, Cu, Zn and Cd.

    PubMed

    Larsen, Finn Krebs; Overgaard, Jacob; Christensen, Mogens; McIntyre, Garry James; Timco, Grigore; Winpenny, Richard E P

    2014-12-01

    The homometallic wheel compound [Cr8F8(O2CCMe3)16] formed with fluorine and pivalic acid ligands can be modified by introducing in the synthesis process a divalent cation M capable of octahedral coordination instead of one of the trivalent Cr centres in the ring. Heterometallic mono-anionic species [Cr7MF8(O2CCMe3)16](-) can form diethylammonium salts and be crystallized from ethylacetate solution as compounds with the general formula [NH2Et2][Cr7MF8((t)BuCO2)16][C4H8O2]0.5 for M = Mn, Fe, Co, Ni, Cu, Zn and Cd. Their structures are isomorphous, belonging to the space group P21/c. The study has determined the degree of order for the individual M heterometal over the possible metal positions of the ring in the crystal structure by modelling based on X-ray diffraction data. The model took into account disorder in tert-butyl groups of the pivalate ligands and in the position and orientation of the ethylacetate solvent molecule. The heterometal turned out to be partly ordered in the crystal structure. PMID:25449616

  15. Spectroscopic and thermal degradation behavior of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes with thiopental sodium anesthesia drug

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.

    2013-04-01

    A new series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized with thiopental sodium anesthesia drug. The elemental analyses of the complexes are confined to stoichiometry of the formulas [M(TPL)3]ṡnH2O (M = Cr(III) or Fe(III); n = 6 or 5), [M(TPL)2(H2O)2]ṡnH2O (M = Mn(II), Co(II) or Ni(II); n = 0 or 4), and [M(TPL)2] (M = Cu(II) or Zn(II); n = 2 or 0) respectively, where TPL is thiopental chelating agent. Structures have been discussed and suggested upon elemental analyses, infrared, Raman, electronic, electron spin resonance, 1H NMR spectral data and magnetic studies. The X-ray powder diffraction (XRD) was performed of metal complexes. The XRD patterns indicate crystalline nature for the complexes. The measured low molar conductance values in dimethylsulfoxide indicate that the complexes are non-electrolyte nature. Spectroscopic discussion refer that coordination take place through three types: Cdbnd N (pyrimidine moiety) nitrogen and C2sbnd S (2-thiolate group) for Cr(III), Mn(II) and Fe(III), C6dbnd O (amido group) oxygen and C2sbnd S (2-thiolate group) for Co(II) and Ni(II), and Cu(II) and Zn(II) ions coordinated via Cdbnd N (pyrimidine moiety) nitrogen, C2dbnd S (2-thiolate group) and C6dbnd O (amido group) oxygen, respectively. The thermal behavior (TG/DTG/DTA) of the complexes was studied and kinetic parameters were determined by Horowitz-Metzger and Coats-Redfern methods. The thiopental and its complexes have been screened for their antimicrobial (G+ and G-) bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa) and fungi (Aspergillus flavus and Candida albicans) activities by minimum inhibitory concentration (MIC) method.

  16. The resistance to cavitation erosion of CrMnN stainless steels

    SciTech Connect

    Fu, W.T.; Jing, T.F.; Zheng, Y.Z.; Yang, Y.B.; Yao, M.

    1998-12-01

    The resistance to cavitation erosion (CE) was measured using a magnetostrictive device and a rotating disk device for some CrMnN stainless steels (Chinese patent ZL 90 1 02197.0). The microstructural changes in the surface layer before and after CE were analyzed by use of Mossbauer spectra. Results show that the resistance to CE of duplex austenitic-martensitic CrMnN stainless steels is much better than that of ZG0Cr13Ni4-6Mo and ZG0Cr16Ni5Mo steel, which are in common use for hydraulic turbine runners. The metastable austenite and its changes in the process of CE are the key factors why the CrMnN stainless steels have excellent resistance to cavitation erosion.

  17. Magnetic anisotropy of Fe{sub 1−y}X{sub y}Pt-L1{sub 0} [X = Cr, Mn, Co, Ni, Cu] bulk alloys

    SciTech Connect

    Cuadrado, R.; Chantrell, R. W.; Klemmer, Timothy J.

    2014-10-13

    We demonstrate by means of fully relativistic first principles calculations that, by substitution of Fe by Cr, Mn, Co, Ni, or Cu in FePt-L1{sub 0} bulk alloys, with fixed Pt content, it is possible to tune the magnetocrystalline anisotropy energy by adjusting the content of the non-magnetic species in the material. The changes in the geometry due to the inclusion of each element induces different values of the tetragonality and hence changes in the magnetic anisotropy and in the net magnetic moment. The site resolved magnetic moments of Fe increase with the X content while those of Pt and X are simultaneously reduced. The calculations are in good quantitative agreement with experimental data and demonstrate that models with fixed band structure but varying numbers of electrons per unit cell are insufficient to describe the experimental data for doped FePt-L1{sub 0} alloys.

  18. Co-precipitation of Ni, Cr, Mn, Pb and Zn in industrial wastewater and sediment samples with copper(II) cyclo-hexylmethyldithiocarbamate for their flame atomic absorption spectrometric determination.

    PubMed

    Ipeaiyeda, Ayodele Rotimi; Odola, Adekunle Johnson

    2012-01-01

    A co-precipitation technique for nickel(II), chromium(II), manganese(II), lead(II) and zinc(II) with the aid of copper(II) cyclo-hexylmethyldithiocarbamate was established. The influences of some analytical parameters such as pH, sample volume, amounts of cyclo-hexylmethyldithiocarbamate and copper(II) on the recovery of metal ions were investigated. The heavy metals in the precipitate were determined by flame atomic absorption spectrophotometry. The range of detection limits for the heavy metals was 0.003-0.005 mg/L. The atomic spectrometric technique with co-precipitation procedure was successfully applied for the determination of Ni, Cr, Mn, Pb and Zn in industrial wastewater and sediment samples from Ladipo stream in Lagos, Nigeria. The mean concentrations for these metals using co-precipitation procedure were not significantly different from corresponding concentrations obtained using spectrometric techniques without co-precipitation procedure. PMID:22678206

  19. Partitioning of Mo, P and other siderophile elements (Cu, Ga, Sn, Ni, Co, Cr, Mn, V, and W) between metal and silicate melt as a function of temperature and silicate melt composition

    NASA Astrophysics Data System (ADS)

    Righter, K.; Pando, K. M.; Danielson, L.; Lee, Cin-Ty

    2010-03-01

    Metal-silicate partition coefficients can provide information about the earliest differentiation histories of terrestrial planets and asteroids. Systematic studies of the effects of key parameters such as temperature and melt composition are lacking for many elements. In particular, data for Mo is scarce, but given its refractory nature, is of great value in interpreting metal-silicate equilibrium. Two series of experiments have been carried out to study Mo and P partitioning between Fe metallic liquid and basaltic to peridotitic silicate melt, at 1 GPa and temperatures between 1500 and 1900 °C. Because the silicate melt utilized was natural basalt, there are also measurable quantities of 9 other siderophile elements (Ni, Co, W, Sn, Cu, Mn, V, Cr, Ga and Zn). The Ni and Co data can be used to assess consistency with previous studies. In addition, the new data also allow a first systematic look at the temperature dependence of Cu, Ga, Sn, Cr, Mn V and W for basaltic to peridotitic melts. Many elements exhibit an increase in siderophile behavior at higher temperature, contrary to popular belief, but consistent with predictions from thermodynamics. Using these new data we examine DMomet/sil and DPmet/sil in detail and show that increasing temperature causes a decrease in the former and an increase in the latter, whereas both increase with MgO content of the silicate melt. The depletions of Mo and P in the mantle of the Earth can be explained by metal-silicate equilibrium at magma ocean conditions — both elements are satisfied at PT conditions of an intermediate depth magma ocean for the Earth 22.5 GPa and 2400 °C.

  20. Effect of Nitrogen Content on Grain Refinement and Mechanical Properties of a Reversion-Treated Ni-Free 18Cr-12Mn Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Behjati, P.; Kermanpur, A.; Najafizadeh, A.; Samaei Baghbadorani, H.; Karjalainen, L. P.; Jung, J.-G.; Lee, Y.-K.

    2014-12-01

    Martensite reversion treatment was utilized to obtain ultrafine grain size in Fe-18Cr-12Mn-N stainless steels containing 0 to 0.44 wt pct N. This was achieved by cold rolling to 80 pct reduction followed by reversion annealing at temperatures between 973 K and 1173 K (700 °C and 900 °C) for 1 to 104 seconds. The microstructural evolution was characterized using both transmission and scanning electron microscopes, and mechanical properties were evaluated using hardness and tensile tests. The steel without nitrogen had a duplex ferritic-austenitic structure and the grain size refinement remained inefficient. The finest austenitic microstructure was achieved in the steels with 0.25 and 0.36 wt pct N following annealing at 1173 K (900 °C) for 100 seconds, resulting in average grain sizes of about 0.240 ± 0.117 and 0.217 ± 0.73 µm, respectively. Nano-size Cr2N precipitates observed in the microstructure were responsible for retarding the grain growth. The reversion mechanism was found to be diffusion controlled in the N-free steel and shear controlled in the N-containing steels. Due to a low fraction of strain-induced martensite in cold rolled condition, the 0.44 wt pct N steel displayed relatively non-uniform, micron-scale grain structure after the same reversion treatment, but it still exhibited superior mechanical properties with a yield strength of 1324 MPa, tensile strength of 1467 MPa, and total elongation of 17 pct. While the high yield strength can be attributed to strengthening by nitrogen alloying, dislocation hardening, and slight grain refinement, the moderate strain-induced martensitic transformation taking place during tensile straining was responsible for enhancement in tensile strength and elongation.

  1. Performance and sulfur poisoning of Ni/CeO2 impregnated La0.75Sr0.25Cr0.5Mn0.5O3-δ anode in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Yiqian; Zhang, Yaohui; Zhu, Xingbao; Wang, Zhihong; Lü, Zhe; Huang, Xiqiang; Zhou, Yongjun; Zhu, Lin; Jiang, Wei

    2015-07-01

    In this study, comparison experiments are conducted based on yttria-stabilized zirconia (YSZ) electrolyte supported single solid oxide fuel cells (SOFCs) with pure La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCrM) or Ni/CeO2 impregnated LSCrM anodes. The single cells are tested in dry H2 and H2/H2S (50 ppm) mixture, respectively. Compared with the pure LSCrM anode, the cell with Ni/CeO2 impregnated LSCrM presents a significant performance improvement when the pure H2 is fueled to the anode, and shows a good stability during a constant-current discharge testing (398 mA cm-2). When the fuel is switched to H2/H2S mixture, the cell with Ni/CeO2 impregnated LSCrM anode still shows a remarkable constant-current discharge (120 mA cm-2) performance compared with pure LSCrM anode. The Ni/CeO2 impregnation can improve the electrochemical performance of the LSCrM anode without any sacrifice of sulfur tolerance ability. The Ni/CeO2 impregnated LSCrM might be a potential anode material for solid oxide fuel cell operating in sulfur-containing fuels. The XRD and XPS results demonstrate that the anode poisoning product is composed of adsorbed sulfur, metal sulfides and sulfate radical. The mass spectrum result confirms that the poisoning mechanism involves the reaction of sulfur with anode rather than the direct reaction between H2S gas and anode.

  2. Electron spin resonance and magnetization studies on Bi0.5Ca0.5Mn0.95TM0.05O3 (TM = Cr, Fe, Co and Ni)

    NASA Astrophysics Data System (ADS)

    Vijayan, D.; Kurian, Joji; Singh, R.

    2012-04-01

    In this work, we present the temperature dependent ESR and magnetization measurements on 3d TM doped Bi-manganite samples of composition Bi0.5Ca0.5Mn0.95TM0.05O3 (TM = Cr, Fe, Co and Ni) synthesized by solid state reaction method. The temperature dependent double integrated intensity (DI) of the ESR signal and the magnetic moment (M) have been used to estimate the charge ordering temperature (TCO), antiferromagnetic ordering (AFM) onset temperature TO and Neel temperature, TN. The 1/DI and 1/M versus T plots show FM correlations in the temperature range T > TCO and coexistence of ferromagnetic (FM) and AFM correlations in the temperature range TCO > T > TO. The magnetization data give TCO values close to the values obtained from ESR data. The data are analyzed in view of electronic phase separation model. The suppression of charge ordering is explained in view of the changes in short range magnetic interactions between Mn ions and the possible change in the band structure as a result of TM ion doping.

  3. Synthesis and characterization of MnCrO4, a new mixed-valence antiferromagnet.

    PubMed

    Nalbandyan, Vladimir B; Zvereva, Elena A; Yalovega, Galina E; Shukaev, Igor L; Ryzhakova, Anastasiya P; Guda, Alexander A; Stroppa, Alessandro; Picozzi, Silvia; Vasiliev, Alexander N; Whangbo, Myung-Hwan

    2013-10-21

    A new orthorhombic phase, MnCrO4, isostructural with MCrO4 (M = Mg, Co, Ni, Cu, Cd) was prepared by evaporation of an aqueous solution, (NH4)2Cr2O7 + 2 Mn(NO3)2, followed by calcination at 400 °C. It is characterized by redox titration, Rietveld analysis of the X-ray diffraction pattern, Cr K edge and Mn K edge XANES, ESR, magnetic susceptibility, specific heat and resistivity measurements. In contrast to the high-pressure MnCrO4 phase where both cations are octahedral, the new phase contains Cr in a tetrahedral environment suggesting the charge balance Mn(2+)Cr(6+)O4. However, the positions of both X-ray absorption K edges, the bond lengths and the ESR data suggest the occurrence of some mixed-valence character in which the mean oxidation state of Mn is higher than 2 and that of Cr is lower than 6. Both the magnetic susceptibility and the specific heat data indicate an onset of a three-dimensional antiferromagnetic order at TN ≈ 42 K, which was confirmed also by calculating the spin exchange interactions on the basis of first principles density functional calculations. Dynamic magnetic studies (ESR) corroborate this scenario and indicate appreciable short-range correlations at temperatures far above TN. MnCrO4 is a semiconductor with activation energy of 0.27 eV; it loses oxygen on heating above 400 °C to form first Cr2O3 plus Mn3O4 and then Mn1.5Cr1.5O4 spinel. PMID:24090277

  4. Correlation of the thermodynamic calculation and the experimental observation of Ni-Mo-Cr low alloy steel changing Ni, Mo, and Cr contents

    NASA Astrophysics Data System (ADS)

    Park, Sang-Gyu; Kim, Min-Chul; Lee, Bong-Sang; Wee, Dang-Moon

    2010-12-01

    SA508 Gr.4N Ni-Mo-Cr low alloy steel has improved fracture toughness and strength compared to commercial low alloy steels such as SA508 Gr.3 Mn-Mo-Ni low alloy steel, which has less than 1% Ni. Higher strength and fracture toughness of low alloy steels can be achieved by increasing the Ni and Cr contents. In this study, the effects of the alloying elements of Ni and Cr on the microstructural characteristics and mechanical properties of SA508 Gr.4N Ni-Mo-Cr low alloy steel are evaluated. Changes in the stable phases of SA508 Gr.4N low alloy steel with these alloying elements were evaluated using thermodynamic calculation software. These values were then compared with the observed microstructural results. Additionally, tensile tests and Charpy impact test were carried out to evaluate the mechanical properties. The thermodynamic calculations show that Ni mainly affects the change of the matrix phase of γ and α rather than the carbide phase. Contrary to the Ni effect, Cr and Mo primarily affect the precipitation behavior of the carbide phases of Cr 23C 6, Cr 7C 3 and Mo 2C. In the microscopic observations, the lath martensitic structure becomes finer as the Ni content increases without affecting the carbides. When the Cr content decreases, the Cr carbide becomes unstable and carbide coarsening occurs. Carbide Mo 2C in the form of fine needles were observed in the high-Mo alloy. Greater strength was obtained after additions of Ni and Mo and the transition properties were improved as the Ni and Cr contents increased. These results were correlated with the thermodynamic calculation results.

  5. Corrosion performance of bi-layer Ni/Cr2C3-NiCr HVAF thermal spray coating

    NASA Astrophysics Data System (ADS)

    Sadeghimeresht, E.; Markocsan, N.; Nylén, P.; Björklund, S.

    2016-04-01

    The corrosion behavior of three HVAF thermal spray coating systems (A: single-layer Ni, B: single-layer Cr2C3-NiCr coatings, and C: bi-layer Ni/Cr2C3-NiCr coating) was comparatively studied using immersion, salt spray, and electrochemical tests. Polarization and EIS results showed that the corrosion behavior of Cr2C3-NiCr coatings in 3.5 wt.% NaCl solution was significantly improved by adding the intermediate layer of Ni. It was illustrated that the polarization resistance of the bi-layer Ni/Cr2C3-NiCr and single-layer Cr2C3-NiCr coatings were around 194 and 38 kΩ cm2, respectively. Microstructure analysis revealed that the bond coating successfully prevented the corrosion propagation toward the coating.

  6. Magnetic coupling in neutral and charged Cr{sub 2}, Mn{sub 2}, and CrMn dimers

    SciTech Connect

    Desmarais, N.; Reuse, F. A.; Khanna, S. N.

    2000-04-01

    Theoretical ab initio studies of neutral, cationic and anionic Cr{sub 2}, Mn{sub 2}, and CrMn dimers have been carried out to explore the progression of magnetic coupling with the number of electrons. It is shown that while Cr{sub 2} and Cr{sub 2}{sup -} have antiferromagnetically coupled atomic spins, Cr{sub 2}{sup +} has a ferromagnetic ground state closely followed by an antiferromagnetic state. On the other hand, all Mn{sub 2} dimers are ferromagnetic, irrespective of the charge. The neutral CrMn is ferrimagnetic while the charged CrMn are antiferromagnetic. In all cases, the charged dimers are found to be more stable than the neutral ones. The results are compared with available calculations and experiments and the difficulties associated with theoretical description and the experimental interpretations are discussed. (c) 2000 American Institute of Physics.

  7. High temperature oxidation resistant coatings for the directionally solidified Ni-Nb-Cr-Al eutectic superalloy

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Ulion, N. E.; Felten, E. J.

    1977-01-01

    Protective coatings required for the Ni-Nb-Cr-Al directionally solidified eutectic superalloy were developed and evaluated on the basis of oxidation resistance, diffusional stability, thermal fatigue, and creep resistance. NiCrAlY+Pt and NiCrAlY physical vapor-deposition coating systems exhibited the best combination of properties. Burner-rig testing indicated that the useful life of a 127-micron-thick NiCrAlY+Pt coating exceeds 1000 h at 1366 K. Eutectic-alloy creep lives at 1311 K and a stress of 151.7 MN/sq m were greater for NiCrAlY+Pt-coated specimens than for uncoated specimens by a factor of two.

  8. Growth and characterization of epitaxial NiMnSb/ZnTe/NiMnSb magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Gerhard, F.; Naydenova, T.; Baussenwein, M.; Schumacher, C.; Gould, C.; Molenkamp, L. W.

    2016-02-01

    The half-metal ferromagnet NiMnSb, with its high spin polarization, low magnetic damping and tunable magnetic anisotropy, is a promising material for applications in spin torque devices. We develop the epitaxial growth of NiMnSb/ZnTe/NiMnSb heterostructures, aiming towards the realization of an all-NiMnSb based magnetic tunneling junction (MTJ). Layers are grown in situ by Molecular Beam Epitaxy (MBE) and Atomic Layer Epitaxy (ALE) methods. By tuning Mn content, the magnetic anisotropy of each of the two NiMnSb layers is adjusted in order to achieve mutually orthogonal uniaxial anisotropies. SQUID measurements of the magnetization along orthogonal crystal directions [110] and [ 1 1 bar 0] confirm that the two layers have mutually orthogonal anisotropy. High Resolution X-Ray Diffraction measurements and simulations confirm the nominal layer stack and demonstrate the high crystalline quality of the individual layers. Such layer stacks provide a potential basis for TMR-based spin-torque devices such as spin-torque oscillators.

  9. Electrodeposition Behavior of Mn with Ni in Acidic Sulfate Solutions

    NASA Astrophysics Data System (ADS)

    Ji, Dan; Le, Xiawen; Zhong, Qingdong; Zhou, Qiongyu

    2014-09-01

    The influence of Mn2+/Ni2+ mole ratio in electrolytes on the Ni-Mn alloy deposits was studied. The electrodeposition mechanism of Mn with Ni is analyzed by the cyclic voltammogram (CV) and an "induced co-deposition" mechanism is proposed for Ni-Mn alloy electrodeposition. The results show that the Mn content in Ni-Mn alloy deposit and the hardness increased with the increase of Mn2+/Ni2+ mole ratio in electrolytes. When the Mn2+/Ni2+ mole ratio in bath was 2/1, the corrosion current density of the deposit coating was the lowest and the corresponding corrosion potential was higher, and under these conditions the coating with a Mn content of 1.20 wt.% showed good corrosion resistance. The scanning electron microscopy (SEM) of the alloy coatings exhibited that the morphology of Ni-Mn alloy coatings were different from Pure Ni coating, and when Mn2+/Ni2+ was 2/1, the surface was compact and homogeneous.

  10. Reactivity of hydrated monovalent first row transition metal ions M(+)(H2O)n, M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, toward molecular oxygen, nitrous oxide, and carbon dioxide.

    PubMed

    van der Linde, Christian; Hemmann, Sonja; Höckendorf, Robert F; Balaj, O Petru; Beyer, Martin K

    2013-02-14

    The reactions of hydrated monovalent transition metal ions M(+)(H(2)O)(n), M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, toward molecular oxygen, nitrous oxide, and carbon dioxide were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Clusters containing monovalent chromium, cobalt, nickel, or zinc were reactive toward O(2), while only hydrated cobalt was reactive toward N(2)O. A strongly size dependent reactivity was observed. Chromium and cobalt react very slowly with carbon dioxide. Nanocalorimetric analysis, (18)O(2) exchange, and collision induced dissociation (CID) experiments were done to learn more about the structure of the O(2) products. The thermochemistry for cobalt, nickel, and zinc is comparable to the formation of O(2)(-) from hydrated electrons. These results suggest that cobalt, nickel, and zinc are forming M(2+)/O(2)(-) ion pairs in the cluster, while chromium rather forms a covalently bound dioxygen complex in large clusters, followed by an exothermic dioxide formation in clusters with n ≤ 5. The results show that hydrated singly charged transition metal ions exhibit highly specific reactivities toward O(2), N(2)O, and CO(2). PMID:22506540

  11. Phase transformation controlled tetragonality of MnNi-based nanocrystals

    NASA Astrophysics Data System (ADS)

    Shen, Jian; Dai, Qilin; Ren, Shenqiang

    2016-03-01

    The phase transformation controlled tetragonality of MnNi nanostructures has attracted wide interest for their shape memory effect. In this study, MnNi nanocrystals were selected to epitaxially grow an FeCo shell, where the antiferromagnetic L10 phase transformation of the MnNi core triggers the tetragonal distortion in the magnetically soft FeCo shell. The tetragonality change of L10 MnNi under thermal annealing enables the control of the tetragonality of the FeCo phase, ultimately increasing magnetocrystalline anisotropy and coercivity. This study opens up a new route to fabricate functional nanostructures with unique magnetic properties.

  12. Phase Transformation and Magnetic Property of Ni-Mn-Ga Powders Prepared by Dry Ball Milling

    NASA Astrophysics Data System (ADS)

    Tian, B.; Chen, F.; Tong, Y. X.; Li, L.; Zheng, Y. F.

    2012-12-01

    This study investigated the phase transformations and magnetic properties of Ni-Mn-Ga alloy powders prepared by dry ball milling in argon atmosphere. The Fe and Cr elements were found to be introduced in the alloy after ball milling, which should result from the severe collision and friction among the particles, balls, and vial. The x-ray diffraction result indicated that the Fe and Cr elements should have alloyed with the Ni-Mn-Ga matrix. The martensitic transformation temperature and Curie temperature of the 800 °C annealed powders decreased by ~33 °C and increased by ~28 °C, respectively, as compared to that of the bulk alloy. The comprehensive effect of the changing of valence electron concentration of the alloy due to the introduction of Fe and Cr and the grain refinement of the alloy caused by ball milling should be responsible for the reduction of martensitic transformation temperature. The saturation magnetization of the 800 °C annealed powders became larger (~5 emu/g) than that of the bulk alloy. The enhancement of magnetic properties, such as the increase of Curie temperature and enhancement of saturation magnetization of the annealed Ni-Mn-Ga powders, should be attributed to the increase of magnetic exchange caused by introduction of Fe in the alloy. The contaminations of Fe and Cr elements emerging from the dry ball milling process changed the phase transformation and magnetic properties of the Ni-Mn-Ga alloy. Therefore, the dry ball milling process is difficult to control the contamination from the milling medium and not suitable to prepare Ni-Mn-Ga powders. On the contrary, the wet ball milling method under liquid medium should be a better method to prevent the contamination and fabricate pure Ni-Mn-Ga ferromagnetic shape memory alloy powders.

  13. CrMn underlayers for CoCrPt thin film media

    SciTech Connect

    Lee, L.L.; Laughlin, D.E.; Lambeth, D.N.

    1998-07-01

    An improved CoCrPt thin film medium or longitudinal magnetic recording which has a coercivity significantly greater than prior CoCrPt thin film media was investigated. A CrMn alloy underlayer was used, instead of the conventional Cr underlayer. A coercivity value of 4,280 Oe was easily reached in a CoCrPt film on a 50 nm thick CrMn underlayer as compared to 2,810 Oe with a pure Cr underlayer. It was found that the coercivity increase due to the Mn addition was realized if the substrates were preheated before the sputtering. Grain boundary interdiffusion of Mn from the underlayer to the magnetic layer may be the cause for the coercivity increase.

  14. X-ray photoelectron spectroscopic analysis of oxidized Fe-16Cr-16Ni-2Mn-1Mo-2Si austenitic stainless steel

    SciTech Connect

    Poston, J.A., Jr.; Siriwardane, R.V.; Dunning, J.S.; Alman, D.E.; Rawers, J.C.

    2007-03-30

    Depth profile analysis (argon ion etching/X-ray photoelectron spectroscopy) was conducted on a series of Fe–16Cr–16Ni–2Mn–1Mo–2Si austenitic stainless steel samples oxidized at 973 and 1073 K with exposure times of 25, 100, 193, 436 and 700 h. Surface and near surface rearrangement following oxidation resulted in a region of high Cr concentration on all oxidized samples. Temperature and time dependence to O2 penetration depth was observed. In general, O2 penetration depth was found to increase with increasing exposure up to 436 h. No increase in depth was observed between 436 and 700 h exposure time.

  15. Thermomagnetic hysteresis effects in NiMn and NiMnPd thin films

    NASA Astrophysics Data System (ADS)

    Öner, Y.; Lue, C. S.; Ross, Joseph H.; Rathnayaka, K. D. D.; Naugle, D. G.

    2001-06-01

    dc magnetization measurements, for zero-field cooled (MZFC) and field-cooled (MFC) cases, have been carried out for flash-evaporated Pd-doped NiMn thin films. These included reentrant phases (Ni76-xPdx)Mn24, for 0⩽x⩽5, and Ni75Mn23Pd2, a pure spinglass phase. The studies were performed over the temperature range 3-300 K. Low-field magnetization measurements show the irreversibility effect (MZFC and MFC diverge) at temperatures below the Curie temperature Tc. In Ni75Mn23Pd2, MZFC falls below MFC, as usually observed. However, in reentrant compositions, MZFC crosses MFC upon warming into the ferromagnetic regime, where it stays above MFC at temperatures below Tc. This unusual behavior is attributed to a model of Imry and Ma in which, in a ferromagnet with antiferromagnetic impurities, the impurities can couple to the host ferromagnetic alignment and force the system to break into domains antiferromagnetically coupled to each other. Field-cooled hysteresis measurements indicate the uniaxial anisotropy in these samples to be small, in contrast with the rigid uniaxial anisotropy reported for the corresponding polycrystalline bulk samples. Since the lattice-orbit coupling is weak in the amorphous phase, this clearly demonstrates that the physical origin of the unidirectional anisotropy is associated with the spin-orbit coupling.

  16. The effect of interstitial carbon on the mechanical properties and dislocation substructure evolution in Fe40.4Ni11.3Mn34.8Al7.5Cr6 high entropy alloys

    DOE PAGESBeta

    Wang, Zhangwei; Baker, Ian; Cai, Zhonghou; Chen, Si; Poplawsky, Jonathan D.; Guo, Wei

    2016-09-01

    A systematic study of the effects of up to 1.1 at. % carbon on the mechanical properties and evolution of the dislocation substructure in a series of a high entropy alloys (HEA) based on Fe40.4Ni11.3Mn34.8Al7.5Cr6 is presented. Transmission electron microscopy (TEM), synchrotron X-ray diffraction (XRD) and atom probe tomography (APT) were used to show that all the alloys are single-phase f.c.c. random solid solutions. The lattice constant, determined from synchrotron XRD measurements, increases linearly with increasing carbon concentration, which leads to a linear relationship between the yield strength and the carbon concentration. The dislocation substructures, as determined by a TEM,more » show a transition from wavy slip to planar slip and, at higher strains, and from cell-forming structure (dislocations cells, cell blocks and dense dislocation walls) to non-cell forming structure (Taylor lattice, microbands and domain boundaries) with the addition of carbon, features related to the increase in lattice friction stress. The stacking fault energy (measured via weak-beam imaging of the separation of dislocation partials) decreases with increasing carbon content, which also contributes to the transition from wavy slip to planar slip. The formation of non-cell forming structure induced by carbon leads to a high degree of strain hardening and a substantial increase in the ultimate tensile strength. In conclusion, the consequent postponement of necking due to the high strain hardening, along with the plasticity accommodation arising from the formation of microbands and domain boundaries, result in an increase of ductility due to the carbon addition.« less

  17. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-09-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  18. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-01-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  19. Microstructure and mechanical behavior of Fe30Ni 20Mn35Al15 and modified Fe30Ni 20Mn35Al15 alloys

    NASA Astrophysics Data System (ADS)

    Meng, Fanling

    A novel alloy with nominal composition Fe30Ni 20Mn35Al15 has been found to show good room-temperature strength and significant ductility. The current project is to study the wear properties of as-cast Fe30Ni20Mn35Al 15 and discuss the possibility of further improving the mechanical properties of this alloy. The dry sliding wear of as-cast Fe30Ni20Mn 35Al15 was studied in in four different environments, i.e. air, dry oxygen, dry argon and a 4% hydrogen/nitrogen mixture. Two-body and three-body abrasive wear mechanism was found for tests in oxygen-containing environments, while plastic flow mechanisms dominated the wear behavior for tests in argon. Hydrogen embrittlement led to 1000% increase of wear loss by causing more rapid crack nucleation of the asperities. The effects of different additions of chromium (≤ 8 at. %) on both microstructure and fracture behavior of Fe30Ni20Mn 35Al15 were investigated. All alloys consisted of (Ni, Al)-rich B2 and (Fe, Mn)-rich f.c.c. phases with most of the Cr residing in the f.c.c. phase. The addition of 6 at. % Cr not only increased the room temperature ductility, but also completely suppressed the environmental embrittlement observed in the Cr-free alloy at low strain rates. The effects of varying the Al concentration on the microstructures and tensile properties of six two-phase FeNiMnAl alloys with a composition close to Fe30Ni20Mn35Al15 were studied. The increase in f.c.c. volume fraction and f.c.c. lamellar width led to an increase in ductility and a decrease in yield strength. The correlation between the yield stress and f.c.c. lamellar spacing lambda obeyed a Hall-Petch-type relationship, i.e. sigmay=252+0.00027lambda-1, where the units for sigmay and lambda are MPa and meter, respectively. FeNiMnAl alloy with B2 and f.c.c. phases aligned along was reported to show high strength at room temperature. The mechanical properties of Fe 28Ni18Mn33Al21, consisting of (Ni, Al)-enriched B2 and (Fe, Mn)-enriched f.c.c. phases with

  20. Ring head recording on perpendicular media: Output spectra for CoCr and CoCr/NiFe media

    NASA Astrophysics Data System (ADS)

    Stubbs, D. P.; Whisler, J. W.; Moe, C. D.; Skorjanec, J.

    1985-04-01

    The recording density response for sputtered CoCr (thickness=0.5 μm) and CoCr/NiFe (t=0.25 μm/0.5 μm) as well as evaporated CoNi (t=0.12 μm) and Co surface-doped iron oxide particulate media has been measured by reading and writing with Mn-Zn ferrite heads (gap length=0.375 μm, track width=37 μm) in contact with the media. Measurements to 200 kfc/i (thousand flux changes per inch) show a gap null around 115 kfc/i. The data have been normalized by dividing out the head sensitivity to obtain the value of spacing plus transition width (d+a) for the various media. For the CoCr media this value varied from 0.075-0.088 μm; for CoNi, 0.100 μm, and for the particulate medium, 0.163 μm. In addition, testing with a larger gapped Mn-Zn ferrite head (g=2.43 μm) shows that the head fields are distorted by the soft magnetic underlayer in dual layer CoCr/NiFe samples when the gap length is large compared to the distance to the underlayer.

  1. Tough cryogenic alloys from the Fe-Mn and Fe-Mn-Cr systems

    NASA Technical Reports Server (NTRS)

    Schanfein, M. J.; Zackay, V. F.; Morris, J. W., Jr.

    1974-01-01

    By adjusting composition, metastable gamma (austenite) and epsilon (hexagonal) martensite may be retained in Fe-Mn and Fe-Mn-Cr alloys and used to impact toughness through the TRIP mechanism. The resulting alloys have excellent toughness at cryogenic temperatures. The best alloys obtained to date are: Fe-20Mn, with sigma (sub y) = 79ksi and K sub IC = 275ksi square root of (in) at 77 K, and Fc-16Mn-8Cr, with sigma sub y = 85ksi and K sub IC = 72ksi square root of (in) at 77 K.

  2. Magnetodielectric coupling in frustrated spin systems: the spinels MCr₂O₄ (M = Mn, Co and Ni).

    PubMed

    Mufti, N; Nugroho, A A; Blake, G R; Palstra, T T M

    2010-02-24

    We have studied the magnetodieletric coupling of polycrystalline samples of the spinels MCr(2)O(4) (M = Mn, Co and Ni). Dielectric anomalies are clearly observed at the onset of the magnetic spiral structure (T(s)) and at the 'lock-in' transition (T(f)) in MnCr(2)O(4) and CoCr(2)O(4), and also at the onset of the canted structure (T(s)) in NiCr(2)O(4). The strength of the magnetodielectric coupling in this system can be explained by spin-orbit coupling. Moreover, the dielectric response in an applied magnetic field scales with the square of the magnetization for all three samples. Thus, the magnetodielectric coupling in this state appears to originate from the P(2)M(2) term in the free energy. PMID:21386397

  3. Enhanced diffusion welding of TD-NiCr sheet.

    NASA Technical Reports Server (NTRS)

    Holko, K. H.; Moore, T. J.

    1972-01-01

    A method termed 'enhanced diffusion welding' has been developed to produce solid-state welds in TD-NiCr (Ni-20Cr-2ThO2) alloy sheet with weld strengths of 100% of the parent metal strength. Diffusion welded joints were made in specially processed TD-NiCr that equaled the tensile-shear and creep-rupture shear strengths of the parent material at 1090 deg C. The following observations have been made: specially processed TD-NiCr is preferred over commercial TD-NiCr for diffusion welding; the weld line can be eliminated when joining specially processed TD-NiCr by 600-grit sanding and electropolishing the faying surfaces prior to welding; and, a two-step weld cycle is preferred for diffusion welding of this alloy.

  4. Structural and physical properties of the ferromagnetic tris-dithiooxalato compounds, A[M(II)Cr(III)(C(2)S(2)O(2))(3)], with A(+) = N(n-C(n)()H(2)(n)(+1))(4)(+) (n = 3-5) and P(C(6)H(5))(4)(+) and M(II) = Mn, Fe, Co, and Ni.

    PubMed

    Bradley, Justin M; Carling, Simon G; Visser, Dirk; Day, Peter; Hautot, Dimitri; Long, Gary J

    2003-02-24

    The structural and magnetic properties of the tris-dithiooxalato salts, A[M(II)Cr(C(2)S(2)O(2))(3)], have been investigated with A(+) = PPh(4)(+), N(n-C(n)()H(2)(n)()(+1))(4)(+), with n = 3-5, where M(II) is Mn, Fe, Co, and Ni. With the exception of A[MnCr(C(2)S(2)O(2))(3)], all the salts are ferromagnets with Curie temperatures, T(c), between 5 and 16 K. In contrast to the corresponding oxalates which are ferromagnetic, the A[MnCr(C(2)S(2)O(2))(3)] compounds are paramagnetic above 2 K. Powder neutron diffraction studies of d(20)-PPh(4)[FeCr(C(2)S(2)O(2))(3)] indicate that no structural phase transitions occur between 2.4 and 285 K and that the coefficient of linear expansion is four times larger for the c-axis than for the a-axis. The crystal structure refined from powder neutron diffraction data confirms the honeycomb layer arrangement observed in the related bimetallic tris-oxalate salts. The Mössbauer spectra reveal that the iron(II) in PPh(4)[FeCr(C(2)S(2)O(2))(3)] is coordinated mainly to six oxygen atoms of the dithiooxalato ligand but with a minor component of sulfur coordination that increases with aging of the sample; the iron(II) is high-spin in both cases. Powder neutron diffraction profiles of d(20)-PPh(4)[FeCr(C(2)S(2)O(2))(3)] below T(c) show magnetic intensity with a q = 0 propagation vector, confirming the presence of ferromagnetic order. PMID:12588130

  5. Effect of dose and temperature parameters of neutron irradiation to maximum damaging dose of 77 dpa on characteristics of porosity formed in steel 0.07C-16Cr-19Ni-2Mo-2Mn-Ti-Si-V-P-B

    NASA Astrophysics Data System (ADS)

    Portnykh, I. A.; Kozlov, A. V.; Panchenko, V. L.

    2014-06-01

    The microstructure of samples of cladding tubes made of steel 0.07C-16Cr-19Ni-2Mo-2Mn-Ti-Si-V-P-B (EK164) irradiated to different damaging doses (up to 77 dpa) in the BN-600 reactor at temperatures from 440 to 600°C has been investigated. Characteristics of radiation porosity formed during irradiation in different temperature intervals have been determined. The dependences of the porosity characteristics on the rate of generation of atomic displacements and temperature of neutron irradiation have been established.

  6. Diffusion kinetics of Cr in spinel: Experimental studies and implications for 53Mn-53Cr cosmochronology

    NASA Astrophysics Data System (ADS)

    Posner, Esther S.; Ganguly, Jibamitra; Hervig, Richard

    2016-02-01

    The 53Mn-53Cr decay system, in which 53Mn decays to 53Cr (t1/2 = 3.7 Ma) has been widely used to construct 53Cr/52Cr vs. 55Mn/52Cr isochrons and thus determine relative ages of early solar system objects or events, assuming that the initial Cr isotopic ratio, (53Cr/52Cr)o, equals (53Mn/52Cr)o. With the primary objective of interpretation of these ages within a diffusion kinetic framework, we have determined the tracer diffusion coefficient of Cr in natural spinels, which are very close to the MgAl2O4 end-member composition, as a function of temperature and oxygen fugacity (f(O2)). It is found that the diffusion coefficient of Cr, D(Cr), in two stocks of spinels (referred to as cut-gems and gem-gravels) with very similar major element chemistry is consistently different, but the data in each stock yield well defined Arrhenius relations that show a difference of log D of 0.6-1.0, depending on temperature, with the D(Cr) in gem-gravel being higher than that in the cut-gem stock. The D(Cr) was found to have a positive dependence on f(O2) in the range of f(O2) of around ±2 log units relative to that of the wüstite-magnetite buffer. The difference in the D(Cr) between the two stocks and the observed D(Cr) vs. f(O2) relation has been explained in terms of a change of point defect concentration resulting from heterovalent substitution of trace elements and equilibration with the imposed f(O2) conditions, respectively. Assuming a homogeneous semi-infinite matrix, the closure temperature (Tc) of Cr diffusion in spinel has been calculated as a function of grain size, cooling rate, peak temperature (To) and f(O2). Also the dependence of D(Cr) and Tc(Cr) on the Cr# (i.e. Cr/(Cr + Al) ratio) has been accounted for using available D(Cr) vs. Cr# data in Suzuki et al. (2008). We argue, on the basis of crystal chemical considerations and available diffusion kinetic data for minerals, that the Tc for Mn should be much lower than that for Cr in spinel, olivine and orthopyroxene, and

  7. Process development for Ni-Cr-ThO2 and Ni-Cr-Al-ThO2 sheet

    NASA Technical Reports Server (NTRS)

    Cook, R. C.; Norris, L. F.

    1973-01-01

    A process was developed for the production of thin gauge Ni-Cr-ThO2 sheet. The process was based on the elevated temperature deposition of chromium onto a wrought Ni-2%ThO2 sheet and subsequent high temperature diffusion heat treatments to minimize chromium concentration gradients within the sheet. The mechanical properties of the alloy were found to be critically dependent on those of the Ni-2%ThO2 sheet. A similar process for the production of a Ni-Cr-Al-ThO2 alloy having improved oxidation resistance was investigated but the non-reproducible deposition of aluminum from duplex Cr/Al packs precluded successful scale-up. The mechanical properties of the Ni-Cr-Al-ThO2 alloys were generally equivalent to the best Ni-Cr-ThO2 alloy produced in the programme.

  8. Oxygen potentials in Ni + NiO and Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4] systems

    SciTech Connect

    Kale, G.M.; Fray, D.J. . Dept. of Mining and Mineral Engineering)

    1994-06-01

    The chemical potential of O for the coexistence of Ni + NiO and Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4] equilibria has been measured employing solid-state galvanic cells, (+) Pt, Cu + Cu[sub 2]O [vert bar][vert bar] (Y[sub 2]O[sub 3])ZrO[sub 2] [vert bar][vert bar] Ni + NiO, Pt (-) and (+) Pt, Ni + NiO [vert bar][vert bar] (Y[sub 2]O[sub 3])ZrO[sub 2] [vert bar][vert bar] Ni + Cr[sub 2]O[sub 3] + NiCr[sub 2]O[sub 4], Pt (-) in the temperature range of 800 to 1,300 K and 1,100 to 1,460 K, respectively. The electromotive force (emf) of both he cells was reversible, reproducible on thermal cycling, and varied linearly with temperature. for the coexistence of the two-phase mixture of Ni + NiO, [Delta][mu][sub O[sub 2

  9. Creep and Toughness of Cryomilled NiAl Containing Cr

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Aikin, Beverly; Salem, Jon

    2000-01-01

    NiAl-AlN + Cr composites were produced by blending cryomilled NiAl powder with approx. 10 vol % Cr flakes. In comparison to the as-consolidated matrices, hot isostatically pressed Cr-modified materials did not demonstrate any significant improvement in toughness. Hot extruded NiAl-AlN+10.5Cr, however, possessed a toughness twice that determine for the base NiAl-AlN alloy. Measurement of the 1200 to 1400 K plastic flow properties revealed that the strength of the composites was completely controlled by the properties of the NiAl-AlN matrices. This behavior could be successfully modeled by the Rule-of-Mixtures, where load is shed from the weak Cr to the strong matrix.

  10. Ni(II) Sorption on Biogenic Mn-Oxides with Varying Mn Octahedral Layer Structure

    SciTech Connect

    Zhu, M.; Ginder-Vogel, M; Sparks, D

    2010-01-01

    Biogenic Mn-oxides (BioMnO{sub x}), produced by microorganisms, possess an extraordinary ability to sequester metals. BioMnO{sub x} are generally layered structures containing varying amounts of Mn(III) and vacant sites in the Mn layers. However the relationship between the varying structure of BioMnO{sub x} and metal sorption properties remains unclear. In this study, BioMnO{sub x} produced by Pseudomonas putida strain GB-1 was synthesized at either pH 6, 7, or 8 in CaCl{sub 2} solution, and Ni(II) sorption mechanisms were determined at pH 7 and at different Ni(II) loadings, using isotherm and extended X-ray absorption fine structure (EXAFS) spectroscopic analyses. Our data demonstrate that Ni(II) sorbs at vacant sites in the interlayer of the BioMnO{sub x} and the maximum Ni(II) sorption capacity increases as the formation pH of BioMnO{sub x} decreases. This relation indicates that the quantity of BioMnO{sub x} vacant sites increases as formation conditions become more acidic, which is in good agreement with our companion study. Contents of the vacant sites were quantitatively estimated based on maximum Ni(II) sorption capacity. Additionally, this study reveals that imidazole groups are involved in Ni(II) binding to biomaterials, and have a higher Ni(II) sorption affinity, but a lower site density compared to carboxyl groups.

  11. Evaluation of Ni-Cr-Base Alloys for SOFC Interconnect Applications

    SciTech Connect

    Yang, Z Gary; Xia, Gordon; Stevenson, Jeffry W.

    2006-10-06

    To further understand the suitability of Ni-Cr-base alloys for solid oxide fuel cell (SOFC) interconnect applications, three commercial Ni-Cr-base alloys, Haynes 230, Hastelloy S and Haynes 242 were selected and evaluated for oxidation behavior under different exposure conditions, scale conductivity and thermal expansion. Haynes 230 and Hastelloy S, which have a relatively high Cr content, formed a thin scale mainly comprised of Cr2O3 and (Mn,Cr,Ni)3O4 spinels under SOFC operating conditions, demonstrating excellent oxidation resistance and a high scale electrical conductivity. In contrast, a thick double-layer scale with a NiO outer layer above a chromia-rich substrate was grown on Haynes 242 in moist air or at the air side of dual exposure samples, indicating limited oxidation resistance for the interconnect application. With a face-centered-cubic (FCC) substrate, all three alloys possess a coefficient of thermal expansion (CTE) that is higher than that of candidate ferritic stainless steels, e.g. Crofer22 APU. Among the three alloys, Haynes 242, which is heavily alloyed with W and Mo and contains a low Cr content, demonstrated the lowest average CTE at 13.1x10-6 K-1 from room temperature to 800oC, but it was also observed that the CTE behavior of Haynes 242 was very nonlinear.

  12. Evaluation of Ni-Cr-base alloys for SOFC interconnect applications

    NASA Astrophysics Data System (ADS)

    Yang, Zhenguo; Xia, Guan-Guang; Stevenson, Jeffry W.

    To further understand the suitability of Ni-Cr-base alloys for solid oxide fuel cell (SOFC) interconnect applications, three commercial Ni-Cr-base alloys, Haynes 230, Hastelloy S and Haynes 242 were selected and evaluated for oxidation behavior under different exposure conditions, scale conductivity and thermal expansion. Haynes 230 and Hastelloy S, which have a relatively high Cr content, formed a thin scale mainly comprised of Cr 2O 3 and (Mn,Cr,Ni) 3O 4 spinels under SOFC operating conditions, demonstrating excellent oxidation resistance and a high scale electrical conductivity. In contrast, a thick double-layer scale with a NiO outer layer above a chromia-rich substrate was grown on Haynes 242 in moist air or at the air side of dual exposure samples, indicating limited oxidation resistance for the interconnect application. With a face-centered-cubic (FCC) substrate, all three alloys possess a coefficient of thermal expansion (CTE) that is higher than that of candidate ferritic stainless steels, e.g. Crofer22 APU. Among the three alloys, Haynes 242, which is heavily alloyed with W and Mo and contains a low Cr content, demonstrated the lowest average CTE at 13.1 × 10 -6 K -1 from room temperature to 800 °C, but it was also observed that the CTE behavior of Haynes 242 was very non-linear.

  13. Effects of Cr and Ni on Interdiffusion and Reaction between U and Fe-Cr-Ni Alloys

    SciTech Connect

    K. Huang; Y. Park; L. Zhou; K.R. Coffey; Y.H. Sohn; B.H. Sencer; J. R. Kennedy

    2014-08-01

    Metallic U-alloy fuel cladded in steel has been examined for high temperature fast reactor technology wherein the fuel cladding chemical interaction is a challenge that requires a fundamental and quantitative understanding. In order to study the fundamental diffusional interactions between U with Fe and the alloying effect of Cr and Ni, solid-to-solid diffusion couples were assembled between pure U and Fe, Fe–15 wt.%Cr or Fe–15 wt.%Cr–15 wt.%Ni alloy, and annealed at high temperature ranging from 580 to 700 °C. The microstructures and concentration profiles that developed from the diffusion anneal were examined by scanning electron microscopy, and X-ray energy dispersive spectroscopy (XEDS), respectively. Thick U6Fe and thin UFe2 phases were observed to develop with solubilities: up to 2.5 at.% Ni in U6(Fe,Ni), up to 20 at.%Cr in U(Fe, Cr)2, and up to 7 at.%Cr and 14 at.% Ni in U(Fe, Cr, Ni)2. The interdiffusion and reactions in the U vs. Fe and U vs. Fe–Cr–Ni exhibited a similar temperature dependence, while the U vs. Fe–Cr diffusion couples, without the presence of Ni, yielded greater activation energy for the growth of intermetallic phases – lower growth rate at lower temperature but higher growth rate at higher temperature.

  14. Structural and magnetic properties of Cu Ni Cr spinel oxides

    NASA Astrophysics Data System (ADS)

    Tovar, M.; Torabi, R.; Welker, C.; Fleischer, F.

    2006-11-01

    The compounds CuCr 2O 4 and NiCr 2O 4 crystallize at room temperature in a tetragonal distorted spinel structure, s.g. I4 1/amd, with axes ratio c/ a<1 and >1, respectively. The distortion is caused by the Jahn-Teller ions Cu 2+ and Ni 2+ which flatten or elongate their surrounding oxygen tetrahedron. CuCr 2O 4 and NiCr 2O 4 form a complete solid solution series Cu 1-xNi xCr 2O 4 where for 0.825< x<0.875 members with orthorhombic symmetry were found. Using neutron powder diffraction and thermal analysis methods several members of the solid solution series were investigated. On cooling, all samples showed a temperature-dependent crystallographic phase transition from cubic to tetragonal symmetry between 865 K (CuCr 2O 4) and 310 K (NiCr 2O 4). The phase Cu 0.15Ni 0.85Cr 2O 4 undergoes a second crystallographic transition to orthorhombic symmetry, space group Fddd, at T=300 K. The neutron diffraction experiments as well as SQUID measurements reveal magnetic ordering of the ions between 150 and 50 K which partially occurs as a two-step mechanism.

  15. Effect of Slag Composition on Inclusions in Si-Deoxidized 18Cr-8Ni Stainless Steels

    NASA Astrophysics Data System (ADS)

    Ren, Ying; Zhang, Lifeng; Fang, Wen; Shao, Shijie; Yang, Jun; Mao, Weidong

    2016-04-01

    Laboratory experiments and thermodynamic calculation for the Si-deoxidized 18Cr-8Ni stainless steel with CaO-Al2O3-SiO2-CaF2-MgO-MnO slag were performed to investigate the effect of slag composition on inclusions in Si-deoxidized 18Cr-8Ni stainless steels. A high-basicity slag improved the cleanness of stainless steel, while a low basicity slag lowered the Al2O3 content in inclusions, lowering the melting temperature of inclusions and improving the deformability of inclusions. Approximately, 15 pct content of MgO in the initial slag was beneficial to reduce the corrosion of refractory and would not influence the composition of inclusions. The Al2O3 in slag should be lowered to a minimum to reduce the Al2O3 content in inclusions in Si-deoxidized 18Cr-8Ni stainless steel. The log X_{{{{Al}}_{ 2} {{O}}_{ 3} }}i + log X_{{MgO}}i - log X_{MnO}i - log X_{{{{SiO}}2 }}i of inclusions was expressed as a linear function of log a_{{{{Al}}_{ 2} {{O}}_{ 3} }}^{{s}} + log a_{{CaO}}^{{s}} - log a_{MnO}^{{s}} - log a_{{{{SiO}}2 }}^{{s}} of the slag, which was used to predict the composition of inclusions based on the activity of Al2O3, CaO, SiO2, and MnO in the slag. Moreover, the equilibrium curve of Al-O and the stability diagram of inclusions in Si-deoxidized 18Cr-8Ni stainless steel at 1873 K (1600 °C) were calculated.

  16. Ni spin switching induced by magnetic frustration in FeMn/Ni/Cu(001)

    SciTech Connect

    Wu, J.; Choi, J.; Scholl, A.; Doran, A.; Arenholz, E.; Hwang, Chanyong; Qiu, Z. Q.

    2009-03-08

    Epitaxially grown FeMn/Ni/Cu(001) films are investigated by Photoemission Electron Microscopy and Magneto-Optic Kerr Effect. We find that as the FeMn overlayer changes from paramagnetic to antiferromagnetic state, it could switch the ferromagnetic Ni spin direction from out-of-plane to in-plane direction of the film. This phenomenon reveals a new mechanism of creating magnetic anisotropy and is attributed to the out-of-plane spin frustration at the FeMn-Ni interface.

  17. High-Performance LiNi0.5Mn1.5O4 Spinel Controlled by Mn3+ Concentration and Site Disorder

    SciTech Connect

    Xiao, Jie; Chen, Xilin; Sushko, P. V.; Sushko, Maria L.; Kovarik, Libor; Feng, Jijun; Deng, Zhiqun; Zheng, Jianming; Graff, Gordon L.; Nie, Zimin; Choi, Daiwon; Liu, Jun; Zhang, Jiguang; Whittingham, M. S.

    2012-03-19

    The influences of Mn3+ ions on the properties of high voltage spinel LiNi0.5Mn1.5O4 is systematically investigated in this work. The content of Mn3+ ions in the spinel is tuned by further annealing of the sample or partially substitution of Ni2+ in the lattice structure. The former decreases the amount of Mn3+ while the latter increases Mn3+ concentration, which has been confirmed by both X-ray diffraction (XRD) and electron diffraction analysis. It has also been experimentally and theoretically proven that Mn3+ ions are directly related to the disordering between Ni2+ and Mn4+ on the octahedral sites in the spinel structure which facilitates the transportation of Li+ ions especially at elevated current densities. An extremely cycling stability as well as good rate capability have been observed in the Cr-substituted spinel confirming that an appropriate amount of Mn3+ ions is the key for a high performance high voltage spinel.

  18. Bioaccumulation of Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn in trophosome and vestimentum of the tube worm Riftia pachyptila from Guaymas basin, Gulf of California

    NASA Astrophysics Data System (ADS)

    Ruelas-Inzunza, J.; Páez-Osuna, F.; Soto, Luis A.

    2005-07-01

    Twenty two specimens of vestimentiferan tube worms Riftia pachyptila were collected from Guaymas Basin. The distribution of ten trace metals in trophosome and vestimentum was investigated. Highest mean concentrations of Co, Cu and Fe were detected in the trophosome; while higher mean levels of Cd, Hg, Mn, Ni, Pb and Zn were measured in the vestimentum. However, the t-student test resulted in significant differences (p<0.05) only in the case of Co. Cd and Fe concentrations in vestimentum increased accordingly with the size of specimens. With respect to vent fluids, extreme uptake seems to be a characteristic of R. pachyptila in the case of Cu and Zn but not for the rest of the analyzed metals. Studies concerning accumulation mechanisms of trace metals in R. pachyptila are needed, particularly on the capacity of this organism to tolerate elevated levels of elements considered as non-essential.

  19. NiCr etching in a reactive gas

    SciTech Connect

    Ritter, J.; Boucher, R.; Morgenroth, W.; Meyer, H. G.

    2007-05-15

    The authors have etched NiCr through a resist mask using Cl/Ar based chemistry in an electron cyclotron resonance etch system. The optimum gas mixture and etch parameters were found for various ratios of Ni to Cr, based on the etch rate, redeposits, and the etch ratio to the mask. The introduction of O{sub 2} into the chamber, which is often used in the etching of Cr, served to both increase and decrease the etch rate depending explicitly on the etching parameters. Etch rates of >50 nm min{sup -1} and ratios of >1 (NiCr:Mask) were achieved for NiCr (80:20). Pattern transfer from the mask into the NiCr was achieved with a high fidelity and without redeposits for a Cl/Ar mix of 10% Ar (90% Cl{sub 2}) at an etch rate of {approx_equal}50 nm min{sup -1} and a ratio of 0.42 (NiCr:ZEP 7000 e-beam mask)

  20. Cyclic creep and fatigue of TD-NiCr (thoria-dispersion-strengthened nickel-chromium), TD-Ni, and NiCr sheet at 1200 C

    NASA Technical Reports Server (NTRS)

    Hirschberg, M. H.; Spera, D. A.; Klima, S. J.

    1972-01-01

    The resistance of thin TD-NiCr sheet to cyclic deformation was compared with that of TD-Ni and a conventional nickel-chromium alloy. Strains were determined by a calibration technique which combines room-temperature strain gage and deflection measurements with high-temperature deflection measurements. Analyses of the cyclic tests using measured tensile and creep-rupture data indicated that the TD-NiCr and NiCr alloy specimens failed by a cyclic creep mechanism. The TD-Ni specimens, on the other hand, failed by a fatigue mechanism.

  1. Microhardness of Ni-Cr alloys under different casting conditions.

    PubMed

    Bauer, José Roberto de Oliveira; Loguercio, Alessandro Dourado; Reis, Alessandra; Rodrigues Filho, Leonardo Eloy

    2006-01-01

    This study evaluated the microhardness of Ni-Cr alloys used in fixed prosthodontics after casting under different conditions. The casting conditions were: (1-flame/air torch) flame made of a gas/oxygen mixture and centrifugal casting machine in a non-controlled casting environment; (2-induction/argon) electromagnetic induction in an environment controlled with argon; (3-induction/vacuum) electromagnetic induction in a vacuum environment; (4-induction/air) electromagnetic induction in a non-controlled casting environment. The 3 alloys used were Ni-Cr-Mo-Ti, Ni-Cr-Mo-Be, and Ni-Cr-Mo-Nb. Four castings with 5 cylindrical, 15 mm-long specimens (diameter: 1.6 mm) in each casting ring were prepared. After casting, the specimens were embedded in resin and polished for Vickers microhardness (VH) measurements in a Shimadzu HMV-2 (1,000 g for 10 s). A total of 5 indentations were done for each ring, one in each specimen. The data was subjected to two-way ANOVA and Tukey's multiple comparison tests (alpha = 0.05). The VH values of Ni-Cr-Mo-Ti (422 +/- 7.8) were statistically higher (p < 0.05) than those of Ni-Cr-Mo-Nb (415 +/- 7.6). The lowest VH values were found for Ni-Cr-Mo-Be (359 +/- 10.7). The VH values obtained in the conditions induction/argon and induction/vacuum were similar (p > 0.05) and lower than the values obtained in the conditions induction/air and flame/air torch (p < 0.05). The VH values in the conditions induction/air and flame/air were similar (p > 0.05). The microhardness of the alloys is influenced by their composition and casting method. The hardness of the Ni-Cr alloys was higher when they were cast with the induction/air and flame/air torch methods. PMID:16729173

  2. Influence of gamma radiation on morphology structure, electrochemical corrosion behavior and hardness of Ni-Cr based alloys

    NASA Astrophysics Data System (ADS)

    El-Bediwi, Abu Bakr; Saad, Mohamed; El-Fallalb, Abeer A.

    This study evaluates the effects of gamma radiation on structure, electrochemical corrosion behavior and Vickers hardness of commercial dental Nikkeli-Kromi-Polttosekoitus [Ni65.2Cr22.5Mo9.5X2.8 (X=Nb, Si, Fe and Mn)] alloy. The corrosion rate of Ni65.2Cr22.5Mo9.5X2.8 (X=Nb, Si, Fe and Mn) alloy with 0.5 M HCl is increased with increasing the exposure rate of gamma radiation. The corrosion resistance of Ni65.2Cr22.5Mo9.5X2.8 (X=Nb, Si, Fe and Mn) is varied and reaches a minimum value at 30 KGy. The corrosion potential value also is varied and reaches its highest value at 30 KGy. The Vickers hardness value of Ni65.2Cr22.5Mo9.5X2.8 (X=Nb, Si, Fe and Mn) alloy is decreased by increasing the gamma radiation dose. Also it is obvious from our results that the effects of gamma radiation at the surface are much higher as compared with deeper parts and the structure of the alloy is changed due to its exposure to gamma radiation.

  3. Effect of 3d transition elements substitution for Ni in Ni2Mn1+xSn1-x on the phase stability and magnetic properties: A first principle investigation

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Shang, Jia-Xiang; Wang, Fu-He; Jiang, Cheng-Bao; Xu, Hui-Bin

    2014-11-01

    In hope of understanding the origin of the 3d-transition elements doping effect on the phase stability and magnetic properties of the ferromagnetic shape memory Heusler alloy Ni-Mn-Sn, the Ni-Z-Mn-Sn system with Z=Ni, Cu, Co, Fe, Mn and Cr is investigated using first-principles calculations. The calculated results show that the energetically favorable magnetic order of the L21 structure is antiferromagnetic for Z=Ni and Cu, and ferromagnetic for the Z=Co, Fe, Mn and Cr. However, for L10 structure, the antiferromagnetic state has an energetical preference for each alloy. Accordingly, a magnetic transition accompanies with the martensite phase transformation and a large change in the magnetic moment can be observed in the alloys with the L21 under the ferromagnetic state, which is mainly dependent on the coupling behaviors of the doped atoms. The weak ferromagnetic coupling between the Ni/Cu and Mn, the strong ferromagnetic coupling between Co/Fe and Mn and the antiferromagnetic coupling between Mn/Cr and Mn play an important role on the magnetic order of L21 structures. Furthermore, the Bethe-Slater model is employed to gain a further understanding and regulation of the coupling behaviors of different doping elements, which is very sensitive to the interatomic distance. These calculated results may help in gaining an insight into the doping behavior of these transition metals and provide some theoretical aid to the material design.

  4. Cr(III) Oxidation Coupled With Microbially-Mediated Mn(II) Oxidation

    SciTech Connect

    Youxian Wu; Baolin Deng

    2006-04-05

    Cr(VI) can be reduced to less toxic and mobile Cr(III) species through abiotic and biological processes. Reductive immobilization of Cr(VI) has been widely explored as a cost effective technology for site remediation; Mn oxides are regarded as primary oxidants for Cr(III) oxidation in the environment; and Generation of Mn oxides from Mn(II) in natural environments is believed to be biologically catalyzed.

  5. Microstructure and twinning in epitaxial NiMnGa films

    SciTech Connect

    Mahnke, Guido J.; Mayr, S. G.; Seibt, M.

    2008-07-01

    Although magnetic shape memory alloys have attracted large scientific interest, miniaturization as single-crystalline thin films is still a greatly unresolved issue. In the present work we investigate the microstructure of epitaxial NiMnGa thin films which are fabricated by sputter deposition on magnesium oxide substrates at elevated temperatures. Transmission and scanning electron microscopy as well as atomic force microscopy studies are employed to relate surface topography to twin formation in 7 M martensitic NiMnGa films. Additional findings include pore formation in substrate proximity as well as minor precipitation with reduced nickel and gallium contents.

  6. CASSCF/CI calculations for first row transition metal hydrides - The TiH(4-phi), VH(5-delta), CrH(6-sigma-plus), MnH(7-sigma-plus), FeH(4,6-delta) and NiH(2-delta) states

    NASA Technical Reports Server (NTRS)

    Walch, S. P.; Bauschlicher, C. W., Jr.

    1983-01-01

    Calculations are performed for the predicted ground states of TiH(4-phi), VH(5-delta), CrH(6-sigma-plus), MnH(7-sigma-plus), Fett(4,6-delta) and NiH(2-delta). For FeH both the 6-delta and 4-delta states are studied, since both are likely candidates for the ground state. The ground state symmetries are predicted based on a combination of atomic coupling arguments and coupling of 4s(2)3d(n) and 4s(1)3d(n+1) terms in the molecular system. Electron correlation is included by a CASSCF/CI (SD) treatment. The CASSCF includes near-degeneracy effects, while correlation of the 3d electrons in included at the CI level.

  7. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    SciTech Connect

    Bates, MK; Jia, QY; Ramaswamy, N; Allen, RJ; Mukerjee, S

    2015-03-12

    We report a Ni-Cr/C electrocatalyst with unpreeedented massactivity for the hydrogen evolution reaction (HER). in alkaline electrolyte. The HER Oietics of numerous binary and ternary Ni-alloys and composite Ni/metal-euride/C samples were evaluated in aquebus 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni-Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to munerous binary dor ternary Ni-alloys, inCluding Ni Mg materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a, sink for the H-ads, intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiO content and that the Cr2O3 appears to stabilize the composite NiO component-under HER conditions (where NiOx would typically be reduced to metallic Ni-0). Furthermore, in contrast to Pt, the Ni(O-x)/Cr2O3 catalyst appears resistant to poisoning by the anion.exchange ionomer (AEI), a serloua consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a: detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI.

  8. Site occupancy trend of Co in Ni2MnIn: Ab initio approach

    NASA Astrophysics Data System (ADS)

    Pal, Soumyadipta; Mahadevan, Priya; Biswas, C.

    2015-06-01

    The trend of site occupation of Co at Ni sites of Ni2MnIn system is studied in austenitic phase having L21 structure by ab initio density functional theory (DFT) calculation. The Co atoms prefer to be at Ni sites rather than Mn site and are ferromagetically coupled with Ni and Mn. The ground state has tetragonal structure for Ni1.5Co0.5MnIn and Ni1.25Co0.75MnIn. The Co tends to form cluster.

  9. Tribological properties of rare earth oxide added Cr 3C 2-NiCr coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Lu, Xinchun; Luo, Jianbin

    2007-02-01

    A novel supersonic plasma spraying was used to prepare rare earth oxide added Cr 3C 2-NiCr coatings. X-ray diffractometer, contact surface profiler, hardness tester, micro-friction and -wear tester, environmental scanning electron microscope equipped with energy dispersive spectroscopy were employed to investigate the phase structure, surface morphology, microhardness, and friction properties of deposited coatings, respectively. The results show that surface roughness, microhardness, brittle fracture, friction extent and wear resistance of rare earth oxide added Cr 3C 2-NiCr coatings are effectively improved compared with that of unadded one. The friction and friction mechanism are also discussed.

  10. Mechanical and Tribological Properties of HVOF-Sprayed (Cr3C2-NiCr+Ni) Composite Coating on Ductile Cast Iron

    NASA Astrophysics Data System (ADS)

    Ksiazek, Marzanna; Boron, Lukasz; Radecka, Marta; Richert, Maria; Tchorz, Adam

    2016-06-01

    The aim of the investigations was to compare the microstructure, mechanical, and wear properties of Cr3C2-NiCr+Ni and Cr3C2-NiCr coatings deposited by HVOF technique (the high-velocity oxygen fuel spray process) on ductile cast iron. The effect of nickel particles added to the chromium carbide coating on mechanical and wear behavior in the system of Cr 3 C 2 -NiCr+Ni/ductile cast iron was analyzed in order to improve the lifetime of coated materials. The structure with particular emphasis of characteristic of the interface in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron was studied using the optical, scanning, and transmission electron microscopes, as well as the analysis of chemical and phase composition in microareas. Experimental results show that HVOF-sprayed Cr3C2-NiCr+Ni composite coating exhibits low porosity, high hardness, dense structure with large, partially molten Ni particles and very fine Cr3C2 and Cr7C3 particles embedded in NiCr alloy matrix, coming to the size of nanocrystalline. The results were discussed in reference to examination of bending strength considering cracking and delamination in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron as well as hardness and wear resistance of the coating. The composite structure of the coating provides the relatively good plasticity of the coating, which in turn has a positive effect on the adhesion of coating to the substrate and cohesion of the composite coating (Cr3C2-NiCr+Ni) in wear conditions.

  11. Mechanical and Tribological Properties of HVOF-Sprayed (Cr3C2-NiCr+Ni) Composite Coating on Ductile Cast Iron

    NASA Astrophysics Data System (ADS)

    Ksiazek, Marzanna; Boron, Lukasz; Radecka, Marta; Richert, Maria; Tchorz, Adam

    2016-07-01

    The aim of the investigations was to compare the microstructure, mechanical, and wear properties of Cr3C2-NiCr+Ni and Cr3C2-NiCr coatings deposited by HVOF technique (the high-velocity oxygen fuel spray process) on ductile cast iron. The effect of nickel particles added to the chromium carbide coating on mechanical and wear behavior in the system of Cr 3 C 2 -NiCr+Ni/ductile cast iron was analyzed in order to improve the lifetime of coated materials. The structure with particular emphasis of characteristic of the interface in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron was studied using the optical, scanning, and transmission electron microscopes, as well as the analysis of chemical and phase composition in microareas. Experimental results show that HVOF-sprayed Cr3C2-NiCr+Ni composite coating exhibits low porosity, high hardness, dense structure with large, partially molten Ni particles and very fine Cr3C2 and Cr7C3 particles embedded in NiCr alloy matrix, coming to the size of nanocrystalline. The results were discussed in reference to examination of bending strength considering cracking and delamination in the system of composite coating (Cr 3 C 2 -NiCr+Ni)/ductile cast iron as well as hardness and wear resistance of the coating. The composite structure of the coating provides the relatively good plasticity of the coating, which in turn has a positive effect on the adhesion of coating to the substrate and cohesion of the composite coating (Cr3C2-NiCr+Ni) in wear conditions.

  12. High-temperature nitridation of Ni-Cr alloys

    NASA Astrophysics Data System (ADS)

    Kodentsov, A. A.; Gülpen, J. H.; Cserháti, C.; Kivilahti, J. K.; van Loo, F. J. J.

    1996-01-01

    The nitriding behavior of nickel-chromium alloys was investigated at 1398 K over the range 1 to 6000 bar of external nitrogen pressure. The morphology of the nitrided zone depends on the concentration of chromium in the initial alloy and the N2 pressure (fugacity) applied upon the system. The transition from CrN to Cr2N precipitation was observed within the reaction zone after nitriding at 100 to 6000 bar of N2 when the chromium content in the initial alloys was 28.0 at. pct or higher. It is shown that the ternary phase π (Cr10Ni7N3) is formed in this system at 1273 K. through a peritectoid reaction between Cr2N and nickel solid solution and becomes unstable above 1373 K. The thermodynamic evaluation of the Ni-Cr-N system was performed and phase equilibria calculated. Evidence for “up hill” diffusion of nitrogen near the reaction front during the internal nitridation of Ni-Cr alloys at 1398 K was found. It was attributed to the relative instability of chromium nitrides and strong Cr-N interaction in the matrix of the Ni-based solid solution within the nitrided zone.

  13. Optimizing NiCr and FeCr HVOF Coating Structures for High Temperature Corrosion Protection Applications

    NASA Astrophysics Data System (ADS)

    Oksa, M.; Metsäjoki, J.

    2015-02-01

    In order to achieve a desired dense structure for coatings employed in high temperature corrosion conditions, thermal spray process optimization with diagnostic tools can be applied. In this study, NiCr (51Ni-46Cr-2Si-1Fe) and FeCr (Fe-19Cr-9W-7Nb-4Mo-5B-2C-2Si-1Mn) powders were sprayed with HVOFGF (gas-fueled) and HVOFLF (liquid-fueled) systems, and the spray processes were monitored with diagnostic tools, including SprayWatch for measuring the temperature and velocity of the spray stream, and in situ coating property (ICP measurement) for measuring the stress state. Various spray parameters were applied to attain the best coating characteristics for high temperature applications. Selected coatings were exposed to high temperature corrosion conditions both in laboratory and actual power plant. The coatings were analyzed by microscopic means and mechanical testing. The application of process-structure-properties-performance methodology with the process monitoring, analysis of the coating characteristics, and results of corrosion performance are presented in this paper.

  14. Discontinuous coarsening behavior of Ni(2)MnAl intermetallic compound during isothermal aging treatment of Fe-Mn-Ni-Al alloys.

    PubMed

    Heo, Yoon-Uk; Takeguchi, Masaki; Furuya, Kazuo; Lee, Hu-Chul

    2010-08-01

    The discontinuous reaction of the Ni(2)MnAl intermetallic phase was investigated during the aging of a solution-treated Fe-8.3Mn-8.2Ni-4.2Al alloy. During aging, Ni(2)MnAl lamellae formed at the prior austenite grain boundaries and twin boundaries and grew into the neighboring grains. The presence of continuously precipitated fine Ni(2)MnAl particles before the growth of the discontinuously precipitated lamellae was confirmed by dark-field transmission electron microscopy, and it was concluded that the present reaction is a type of discontinuous coarsening process, alpha' + Ni(2)MnAl (continuous precipitation) --> alpha + Ni(2)MnAl (discontinuous coarsening). The chemical driving force and the reduction of the total coherent strain energy were suggested to be the driving force for the discontinuous coarsening reaction. PMID:20551447

  15. Cr(OH)₃(s) Oxidation Induced by Surface Catalyzed Mn(II) Oxidation

    SciTech Connect

    Namgung, Seonyi; Kwon, M.; Qafoku, Nikolla; Lee, Gie Hyeon

    2014-09-16

    This study examined the feasibility of Cr(OH)₃(s) oxidation mediated by surface catalyzed Mn(II) oxidation under common groundwater pH conditions as a potential pathway of natural Cr(VI) contaminations. Dissolved Mn(II) (50 μM) was reacted with or without synthesized Cr(OH)₃(s) (1.0 g/L) at pH 7 – 9 under oxic or anoxic conditions. In the absence of Cr(OH)₃(s), homogeneous Mn(II) oxidation by dissolved O₂ was not observed at pH ≤ 8.0 for 50 d. At pH 9.0, by contrast, dissolved Mn(II) was completely removed within 8 d and precipitated as hausmannite. When Cr(OH)₃(s) was present, this solid was oxidized and released substantial amounts of Cr(VI) as dissolved Mn(II) was added into the suspension at pH ≥ 8.0 under oxic conditions. Our results suggest that Cr(OH)₃(s) was readily oxidized by a newly formed Mn oxide as a result of Mn(II) oxidation catalyzed on Cr(OH)₃(s) surface. XANES analysis of the residual solids after the reaction between 1.0 g/L Cr(OH)₃(s) and 204 μM Mn(II) at pH 9.0 for 22 d revealed that the product of surface catalyzed Mn(II) oxidation resembled birnessite. The rate and extent of Cr(OH)₃(s) oxidation was likely controlled by those of surface catalyzed Mn(II) oxidation as the production of Cr(VI) increased with increasing pH and initial Mn(II) concentrations. This study evokes the potential environmental hazard of sparingly soluble Cr(OH)₃(s) that can be a source of Cr(VI) in the presence of dissolved Mn(II).

  16. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    PubMed Central

    Bates, Michael K.; Jia, Qingying; Ramaswamy, Nagappan; Allen, Robert J.; Mukerjee, Sanjeev

    2015-01-01

    We report a Ni–Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline electrolyte. The HER kinetics of numerous binary and ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni–Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to numerous binary and ternary Ni-alloys, including Ni–Mo materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a sink for the Hads intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiOx content and that the Cr2O3 appears to stabilize the composite NiOx component under HER conditions (where NiOx would typically be reduced to metallic Ni0). Furthermore, in contrast to Pt, the Ni(Ox)/Cr2O3 catalyst appears resistant to poisoning by the anion exchange ionomer (AEI), a serious consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI. PMID:26191118

  17. Erosion Performance of HVOF-Sprayed Cr3C2-NiCr Coatings

    NASA Astrophysics Data System (ADS)

    Ji, Gang-Chang; Li, Chang-Jiu; Wang, Yu-Yue; Li, Wen-Ya

    2007-12-01

    Cr3C2-NiCr coatings were deposited by high-velocity oxygen fuel (HVOF) spraying process under spray conditions of different flows of oxygen and propane gases, and spray distances. The orthogonal regression experimental design method was used for systematic investigation of the influence of spray parameters on the erosion performance of Cr3C2-NiCr coatings. Erosion tests were performed at different jet angles of abrasive particles. The erosion mechanism of Cr3C2-NiCr coatings was examined through the surface morphology and cross-sectional microstructure of the eroded coatings. The correlations of the carbide particle size and carbide content with the erosion rate were examined. It was found that the erosion occurred dominantly by spalling of splats from the lamellar interfaces. The spalling resulted from the propagation of cracks parallel to the interfaces between the lamellae exposed to the surface and underlying coating. The carbide particle size and content in the coating influenced significantly the erosion performance of Cr3C2-NiCr coatings.

  18. Magnetic properties of nanocrystalline Ni-Zn, Zn-Mn, and Ni-Mn ferrites synthesized by reverse micelle technique

    NASA Astrophysics Data System (ADS)

    Gubbala, S.; Nathani, H.; Koizol, K.; Misra, R. D. K.

    2004-05-01

    Nanocrystalline nickel-zinc, zinc-manganese, and nickel-manganese ferrites synthesized by reverse micelle synthesis technique were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction, and the magnetic behavior studied by Superconducting Quantum Interference Device. The mixed (Ni-Zn, Zn-Mn, and Ni-Mn) ferrites exhibit blocking temperatures of 11, 20, and 15 K, respectively. The small differences in the blocking temperatures are attributed to the magnetocrystalline anisotropy and L-S coupling. The saturation magnetization of nanocrystalline Ni-Zn, Zn-Mn, and Ni-Mn at 300 K was 4.5, 9, and 7 emu/g, respectively, and at 2 K was 15, 19, and 14 emu/g, respectively. The lower saturation magnetization of the nanocrystalline ferrites compared to their bulk counterparts is attributed to the core-shell morphology of the particles consisting of ferromagnetically aligned core spins and a spin-glass-like surface layer.

  19. Dimensional effects in Ni-Cr multilayered thin films

    NASA Astrophysics Data System (ADS)

    Stearns, M. B.; Lee, C. H.

    1987-04-01

    The dimensionality of Ni-Cr multilayered structures (MLS) was studied from the variation of the temperature dependence of the saturation magnetization Ms with the Ni layer thickness. Since NiCr alloys containing more than 12% Cr are nonmagnetic the thickness of the interfaces and pure Ni regions can be obtained from the measured value of Ms by modeling the MLS and determining the thickness of the pure Ni regions. Assuming that the pure Ni regions are isolated sufficiently to behave independently, comparison was made with several theories. It was found that the observed behavior is similar to that described by the theory of Davis and Keffer with a surface anisotropy energy of about 0.1 that of the exchange energy. This theory uses nonperiodic boundary conditions and assumes a surface anisotropy field which causes the partial pinning of the surface spins. The magnetization decrease calculated with this theory falls off less rapidly with film thickness than other theories. At high fields the magnetization and Curie temperatures of the MLS having 20 Å or less of Ni is found to be field dependent. This is indicative that a considerable amount of the magnetic moments arise from itinerant d electrons.

  20. Alloying effects on the microstructure and phase stability of Fe-Cr-Mn steels

    SciTech Connect

    Rawers, J.C.

    2008-05-01

    Austenitic Fe–Cr–Mn stainless steels interstitially alloyed with nitrogen have received considerable interest lately, due to their many property improvements over conventional Fe–Cr–Ni alloys. The addition of nitrogen to Fe–Cr–Mn stabilizes the fcc structure and increases the carbon solubility. The benefits of increased interstitial nitrogen and carbon content include: enhanced strength, hardness, and wear resistance. This study examines the effect of carbon, silicon, molybdenum, and nickel additions on the phase stability and tensile behavior of nitrogen-containing Fe–Cr–Mn alloys. Nitrogen and carbon concentrations exceeding 2.0 wt.% were added to the base Fe–18Cr–18Mn composition without the formation of nitride or carbide precipitates. Minor additions of molybdenum, silicon, and nickel did not affect nitrogen interstitial solubility, but did reduce carbon solubility resulting in the formation of M23C6 (M=Cr, Fe, Mo) carbides. Increasing the interstitial content increases the lattice distortion strain, which is directly correlated with an increase in yield stress.

  1. Observations on the oxidation of Mn-modified Ni-base Haynes 230 alloy under SOFC exposure conditions

    SciTech Connect

    Yang, Z Gary; Xia, Gordon; Stevenson, Jeffry W.; Singh, Prabhakar

    2005-07-01

    The commercial Ni-base Haynes 230 alloy (Ni-Cr-Mo-W-Mn) was modified with two increased levels of Mn (1 and 2 wt per cent) and evaluated for its oxidation resistance under simulated SOFC interconnect exposure conditions. Oxidation rate, oxide morphology, oxide conductivity and thermal expansion were measured and compared with commercial Haynes 230. It was observed that additions of higher levels of Mn to the bulk alloy facilitated the formation of a bi-layered oxide scale that was comprised of an outer M3O4 (M=Mn, Cr, Ni) spinel-rich layer at the oxide – gas interface over a Cr2O3-rich sub-layer at the metal – oxide interface. The modified alloys showed higher oxidation rates and the formation of thicker oxide scales compared to the base alloy. The formation of a spinel-rich top layer improved the scale conductivity, especially during the early stages of the oxidation, but the higher scale growth rate resulted in an increase in the area-specific electrical resistance over time. Due to their face-centered cubic crystal structure, both commercial and modified alloys demonstrated a coefficient of thermal expansion that was higher than that of typical anode-supported and electrolyte-supported SOFCs.

  2. Cyanide-bridged NiCr and alternate NiFe-NiCr magnetic ultrathin films on functionalized Si(100) surface.

    PubMed

    Tricard, Simon; Costa-Coquelard, Claire; Mazerat, Sandra; Rivière, Eric; Huc, Vincent; David, Christophe; Miserque, Frédéric; Jegou, Pascale; Palacin, Serge; Mallah, Talal

    2012-04-21

    Sequential growth in solution (SGS) was performed for the magnetic cyanide-bridged network obtained from the reaction of Ni(H(2)O)(2+) and Cr(CN)(6)(3-) (referred to as NiCr) on a Si(100) wafer already functionalized by a Ni(II) complex. The growth process led to isolated dots and a low coverage of the surface. We used the NiFe network as a template to improve the growth of the magnetic network. We elaborated alternate NiFe (paramagnetic)-NiCr (ferromagnetic) ultrathin films around 6 nm thick. The magnetic behaviour confirmed the alternate structure with the ferromagnetic zones isolated between the paramagnetic ones since the evolution of the blocking temperature is consistent with the evolution of the layers' thickness expected from the SGS process. PMID:22344390

  3. Hydrogen-Resistant Fe/Ni/Cr-Base Superalloy

    NASA Technical Reports Server (NTRS)

    Bhat, Biliyar N.; Chen, Po-Shou; Panda, Binayak

    1994-01-01

    Strong Fe/Ni/Cr-base hydrogen- and corrosion-resistant alloy developed. Superalloy exhibits high strength and exceptional resistance to embrittlement by hydrogen. Contains two-phase microstructure consisting of conductivity precipitated phase in conductivity matrix phase. Produced in wrought, weldable form and as castings, alloy maintains high ductility and strength in air and hydrogen. Strength exceeds previously known Fe/Cr/Ni hydrogen-, oxidation-, and corrosion-resistant alloys. Provides higher strength-to-weight ratios for lower weight in applications as storage vessels and pipes that must contain hydrogen.

  4. V, Cr, and Mn in the earth, moon, EPB, and SPB and the origin of the moon - Experimental studies

    NASA Technical Reports Server (NTRS)

    Drake, Michael J.; Capobianco, Christopher J.; Newsom, Horton E.

    1989-01-01

    The abundances of V, Cr, and Mn inferred for the mantles of the earth and moon decrease in that order and are similar in both mantles (but distinct from those in the mantles of the Eucrite Parent Body and Shergottite Parent Body), suggesting a common origin for the mantles of the earth and the moon. This hypothesis was investigated on the basis of a comparison between the depletions of V, Cr, and Mn in the mantles of the earth and the moon, and the metal/silicate partition coefficients of these elements at 1260 C and 1 bar pressure among a S-bearing metallic liquid, a silicate melt, and a FeNi alloy. It was found that the earth and the moon depletions of V, Cr, and Mn are not correlated with metal/silicate partition coefficients; the V and Cr partitioned into S-rich metallic liquids under reducing conditions more strongly than Mn, consistent with the relative volatilities of these elements. This indicates that the depletion patterns of these elements in the mantles of the earth and moon cannot be attributed primarily to terrestrial core formation.

  5. Evaporative segregation in 80% Ni-20% Cr and 60% Fe-40% Ni alloys

    NASA Technical Reports Server (NTRS)

    Gupta, K. P.; Mukherjee, J. L.; Li, C. H.

    1974-01-01

    An analytical approach is outlined to calculate the evaporative segregation behavior in metallic alloys. The theoretical predictions are based on a 'normal' evaporation model and have been examined for Fe-Ni and Ni-Cr alloys. A fairly good agreement has been found between the predicted values and the experimental results found in the literature.

  6. Magnetism of hexagonal Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials

    SciTech Connect

    Fuglsby, R.; Kharel, P.; Zhang, W.; Sellmyer, D. J.; Valloppilly, S.; Huh, Y.

    2015-05-07

    Mn{sub 1.5}X{sub 0.5}Sn (X = Cr, Mn, Fe, Co) nanomaterials in the hexagonal Ni{sub 2}In-type crystal structure have been prepared using arc-melting and melt spinning. All the rapidly quenched Mn{sub 1.5}X{sub 0.5}Sn alloys show moderate saturation magnetizations with the highest value of 458 emu/cm{sup 3} for Mn{sub 1.5}Fe{sub 0.5}Sn, but their Curie temperatures are less than 300 K. All samples except the Cr containing one show spin-glass-like behavior at low temperature. The magnetic anisotropy constants calculated from the high-field magnetization curves at 100 K are on the order of 1 Merg/cm{sup 3}. The vacuum annealing of the ribbons at 550 °C significantly improved their magnetic properties with the Curie temperature increasing from 206 K to 273 K for Mn{sub 1.5}Fe{sub 0.5}Sn.

  7. Characterization of the surface of Fe-19Mn-18Cr-C-N during heat treatment in a high vacuum - An XPS study

    SciTech Connect

    Zumsande, K.; Weddeling, A.; Hryha, E.; Huth, S.; Nyborg, L.; Weber, S.; Krasokha, N.; Theisen, W.

    2012-09-15

    Nitrogen-containing CrMn austenitic stainless steels offer evident benefits compared to CrNi-based grades. The production of high-quality parts by means of powder metallurgy could be an appropriate alternative to the standard molding process leading to improved properties. The powder metallurgical production of CrMn austenitic steel is challenging on account of the high oxygen affinity of Mn and Cr. Oxides hinder the densification processes and may lower the performance of the sintered part if they remain in the steel after sintering. Thus, in evaluating the sinterability of the steel Fe-19Mn-18Cr-C-N, characterization of the surface is of great interest. In this study, comprehensive investigations by means of X-ray photoelectron spectroscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy were performed to characterize the surface during heat treatment in a high vacuum. The results show a shift of oxidation up to 600 Degree-Sign C, meaning transfer of oxygen from the iron oxide layer to Mn-based particulate oxides, followed by progressive reduction and transformation of the Mn oxides into stable Si-containing oxides at elevated temperatures. Mass loss caused by Mn evaporation was observed accompanied by Mn oxide decomposition starting at 700 Degree-Sign C. - Highlights: Black-Right-Pointing-Pointer Surface characterization by means of XPS, SEM, and EDX analyses. Black-Right-Pointing-Pointer Heat treatment of a high CrMn powder. Black-Right-Pointing-Pointer Transfer of oxygen from the iron oxide layer to manganese-based particulate oxides. Black-Right-Pointing-Pointer Progressive reduction of Mn oxides. Black-Right-Pointing-Pointer Transformation of the Mn oxides into stable Si-containing oxides.

  8. Microstructural Development and Ternary Interdiffusion in Ni-Mn-Ga Alloys

    NASA Astrophysics Data System (ADS)

    Zhou, Le; Kammerer, Catherine; Giri, Anit; Cho, Kyu; Sohn, Yongho

    2015-12-01

    NiMnGa alloys functioning as either ferromagnetic shape memory alloys or magnetocaloric materials have both practical applications and fundamental research value. In this study, solid-to-solid diffusion couple experiments were carried out to investigate the phase equilibria, microstructural development, and interdiffusion behavior in Ni-Mn-Ga ternary alloys. Selected diffusion couples between pure Ni, Ni25Mn75 and four ternary off-stoichiometric NiMnGa alloys ( i.e., Ni52Mn18Ga30, Ni46Mn30Ga24, Ni52Mn30Ga18, Ni58Mn18Ga24) were assembled and annealed at 1073 K, 1123 K, and 1173 K (800 °C, 850 °C, and 900 °C) for 480, 240, and 120 hours, respectively. At these high temperatures, the β NiMnGa phase has a B2 crystal structure. The microstructure of the interdiffusion zone was examined by scanning electron microscopy and transmission electron microscopy. Concentration profiles across the interdiffusion zone were determined by electron probe micro analysis. Solubility values obtained for various phases were mostly consistent with the existing isothermal phase diagrams, but the phase boundary of the γ(Mn) + β two-phase region was slightly modified. In addition, equilibrium compositions for the γ(Ni) and α' phases at 1173 K (900 °C) were also determined for the respective two-phase region. Both austenitic and martensitic phases were found at room temperature in each diffusion couple with a clear boundary. The compositions at the interfaces corresponded close to valence electron concentration (e/a) of 7.6, but trended to lower values when Mn increased to more than 35 at. pct. Average effective interdiffusion coefficients for the β phase over different compositional ranges were determined and reported in the light of temperature-dependence. Ternary interdiffusion coefficients were also determined and examined to assess the ternary diffusional interactions among Ni, Mn, and Ga. Ni was observed to interdiffuse the fastest, followed by Mn then Ga. Interdiffusion flux

  9. Microstructure and crack resistance of low carbon Cr-Ni and Cr-Ni-W steel after austempering

    NASA Astrophysics Data System (ADS)

    Avdjieva, Tatyana B.; Tsutsumanova, Gichka G.; Russev, Stoyan N.; Staevski, Konstantin G.

    2013-09-01

    The microstructure of the low carbon Cr-Ni steel after slow cooling from austenization temperature represents a mix of granulated bainite with islands from carbon-rich martensite and carbon-poor austenite. After quick cooling throwing in salt bath from austenization temperature the microstructure is lath bainite. However, in the same treatment conditions, the microstructure of the low carbon Cr-Ni-W steel is different — clusters consist from lath ferrite and retained austenite, disposed in the frame of parent's austenite grains. The cooling velocity has no effect upon the structure making. The impact toughness of the steel with tungsten content is bigger than the steel without tungsten.

  10. Creep and oxidation behavior of modified CF8C-plus with W, Cu, Ni, and Cr

    DOE PAGESBeta

    Unocic, Kinga A.; Dryepondt, Sebastien N.; Yamamoto, Yukinori; Maziasz, Philip J.

    2016-02-01

    Here, the microstructures of modified CF8C-Plus (Fe-19Cr-12Ni-0.4W-3.8Mn-0.2Mo-0.6Nb-0.5Si-0.9C) with W and Cu (CF8CPWCu) and CF8CPWCu enhanced with 21Cr + 15Ni or 22Cr + 17.5Ni were characterized in the as-cast condition and after creep testing. When imaged at lower magnifications, the as-cast microstructure was similar among all three alloys as they all contained a Nb-rich interdendritic phase and Mn-based inclusions. Transmission electron microscopy (TEM) analysis showed the presence of nanoscale Cu-rich nanoprecipitates distributed uniformly throughout the matrix of CF8CPWCu, whereas in CF8CPWCu22/17, Cu precipitates were found primarily at the grain boundaries. The presence of these nanoscale Cu-rich particles, in addition to W-richmore » Cr23C6, nanoscale Nb carbides, and Z-phase (Nb2Cr2N2), improved the creep strength of the CF8CPWCu steel. Modification of CF8CPWCu with Cr and Ni contents slightly decreased the creep strength but significantly improved the oxidation behavior at 1073 K (800 °C). In particular, the addition of 22Cr and 17.5Ni strongly enhanced the oxidation resistance of the stainless steel resulting in a 100 degrees or greater temperature improvement, and this composition provided the best balance between improving both mechanical properties and oxidation resistance.« less

  11. Creep and Oxidation Behavior of Modified CF8C-Plus with W, Cu, Ni, and Cr

    NASA Astrophysics Data System (ADS)

    Unocic, Kinga A.; Dryepondt, Sebastien; Yamamoto, Yukinori; Maziasz, Philip J.

    2016-04-01

    The microstructures of modified CF8C-Plus (Fe-19Cr-12Ni-0.4W-3.8Mn-0.2Mo-0.6Nb-0.5Si-0.9C) with W and Cu (CF8CPWCu) and CF8CPWCu enhanced with 21Cr + 15Ni or 22Cr + 17.5Ni were characterized in the as-cast condition and after creep testing. When imaged at lower magnifications, the as-cast microstructure was similar among all three alloys as they all contained a Nb-rich interdendritic phase and Mn-based inclusions. Transmission electron microscopy (TEM) analysis showed the presence of nanoscale Cu-rich nanoprecipitates distributed uniformly throughout the matrix of CF8CPWCu, whereas in CF8CPWCu22/17, Cu precipitates were found primarily at the grain boundaries. The presence of these nanoscale Cu-rich particles, in addition to W-rich Cr23C6, nanoscale Nb carbides, and Z-phase (Nb2Cr2N2), improved the creep strength of the CF8CPWCu steel. Modification of CF8CPWCu with Cr and Ni contents slightly decreased the creep strength but significantly improved the oxidation behavior at 1073 K (800 °C). In particular, the addition of 22Cr and 17.5Ni strongly enhanced the oxidation resistance of the stainless steel resulting in a 100 degrees or greater temperature improvement, and this composition provided the best balance between improving both mechanical properties and oxidation resistance.

  12. How Deep and Hot was Earth's Magma Ocean? Combined Experimental Datasets for the Metal-silicate Partitioning of 11 Siderophile Elements - Ni, Co, Mo, W, P, Mn, V, Cr, Ga, Cu and Pd

    NASA Technical Reports Server (NTRS)

    Righter, Kevin

    2008-01-01

    variable oxygen fugacity. Preliminary results confirm that D(Ni) and D(Co) converge at pressures near 25-30 GPa and approximately 2200 K, and show that D(Pd) and D(Cu) become too low at the PT conditions of the deepest models. Furthermore, models which force fit V and Cr mantle concentrations by metal-silicate equilibrium overlook the fact that at early Earth mantle fO2, these elements will be more compatible in Mg-perovskite and (Fe,Mg)O than in metal. Thus an intermediate depth magma ocean, at 25-30 GPa, 2200 K, and at IW-2, can explain more mantle siderophile element concentrations than other models.

  13. How Deep and Hot was Earth's Magma Ocean? Combined Experimental Datasets for the Metal-Silicate Partitioning of 11 Siderophile Elements - Ni, Co, Mo, W, P, Mn, V, Cr, Ga, Cu and Pd.

    NASA Astrophysics Data System (ADS)

    Righter, K.

    2008-12-01

    oxygen fugacity. Preliminary results confirm that D(Ni) and D(Co) converge at pressures near 25-30 GPa and ~2200 K, and show that D(Pd) and D(Cu) become too low at the PT conditions of the deepest models. Furthermore, models which force fit V and Cr mantle concentrations by metal-silicate equilibrium overlook the fact that at early Earth mantle fO2, these elements will be more compatible in Mg-perovskite and (Fe,Mg)O than in metal. Thus an intermediate depth magma ocean, at 25-30 GPa, 2200 K, and at IW-2, can explain more mantle siderophile element concentrations than other models.

  14. Magnetodielectric effect in Bi2NiMnO6-La2NiMnO6 superlattices

    NASA Astrophysics Data System (ADS)

    Padhan, P.; LeClair, P.; Gupta, A.; Subramanian, M. A.; Srinivasan, G.

    2009-07-01

    Multilayer superlattices consisting of multiferroic Bi2NiMnO6 (BNMO) and La2NiMnO6 (LNMO) have been grown heteroepitaxially on pure and Nb-doped SrTiO3 substrates using the pulsed laser deposition technique. In a series of superlattice structures grown with a fixed BNMO layer thickness of ten unit cells, we find that the c-axis lattice parameter, Curie temperature and magnetocapacitance are strongly dependent upon the number of stacked LNMO unit cells in the repeating units. The thickness-dependent magnetodielectric effect is attributed to the fluctuations in electric and magnetic dipole ordering due to the substrate and interface induced stress in the superlattice structures. An enhanced magnetodielectric effect in multilayers with LNMO thicknesses larger than six unit cells is explained based on possible canting of spin at the interfaces of LNMO and BNMO.

  15. A comparative study of magnetic behaviors in TbNi{sub 2}, TbMn{sub 2} and TbNi{sub 2}Mn

    SciTech Connect

    Wang, J. L.; Md Din, M. F.; Hong, F.; Cheng, Z. X.; Dou, S. X.; Kennedy, S. J.; Studer, A. J.; Campbell, S. J.; Wu, G. H.

    2014-05-07

    All TbNi{sub 2}, TbMn{sub 2}, and TbNi{sub 2}Mn compounds exhibit the cubic Laves phase with AB{sub 2}-type structure in spite of the fact that the ratio of the Tb to transition-metal components in TbNi{sub 2}Mn is 1:3. Rietveld refinement indicates that in TbNi{sub 2}Mn the Mn atoms are distributed on both the A (8a) and B (16d) sites. The values of the lattice constants were measured to be a = 14.348 Å (space group F-43 m), 7.618 Å, and 7.158 Å (space group Fd-3 m) for TbNi{sub 2}, TbMn{sub 2}, and TbNi{sub 2}Mn, respectively. The magnetic transition temperatures T{sub C} were found to be T{sub C} = 38 K and T{sub C} = 148 K for TbNi{sub 2} and TbNi{sub 2}Mn, respectively, while two magnetic phase transitions are detected for TbMn{sub 2} at T{sub 1} = 20 K and T{sub 2} = 49 K. Clear magnetic history effects in a low magnetic field are observed in TbMn{sub 2} and TbNi{sub 2}Mn. The magnetic entropy changes have been obtained.

  16. Structure and Tribological Characteristics of HVOF Coatings Sprayed from Powder Blends of Cr3C2-25NiCr and NiCrBSi Alloy

    NASA Astrophysics Data System (ADS)

    Määttä, A.; Kanerva, U.; Vuoristo, P.

    2011-01-01

    HVOF spraying was used to prepare coatings from mechanical blends of Cr3C2-25NiCr and NiCrBSi powders. The aim of this study is to study the tribological behavior of coatings prepared from such powder blends. The coatings were studied under dry sliding conditions particularly at high temperatures. Tribological properties of the coatings were characterized using a specific hot-button tribological tester at the temperature of 300 °C in air, and a pin-on-disk test at room temperature. Addition of NiCrBSi resulted in coatings, which showed low coefficient of friction in high temperatures, and in high levels of contact pressure and sliding speed.

  17. Order-disorder transitions in NiCr 2S 4

    NASA Astrophysics Data System (ADS)

    Vaqueiro, P.; Powell, A. V.; Lebech, B.

    2000-03-01

    Order-disorder transitions in NiCr 2S 4 have been investigated by high-temperature powder neutron diffraction. At 835(5)°C, NiCr 2S 4 transforms from the monoclinic Cr 3S 4 structure to a hexagonal cation-deficient NiAs structure.

  18. Precipitation and fracture behaviour of Fe-Mn-Ni-Al alloys

    NASA Astrophysics Data System (ADS)

    Heo, Yoon-Uk; Lee, Hu-Chul

    2013-12-01

    The effects of Al addition on the precipitation and fracture behaviour of Fe-Mn-Ni alloys were investigated. With the increasing of Al concentration, the matrix and grain boundary precipitates changed from L10 θ-MnNi to B2 Ni2MnAl phase, which is coherent and in cube-to-cube orientation relationship with the α‧-matrix. Due to the suppression of the θ-MnNi precipitates at prior austenite grain boundaries (PAGBs), the fracture mode changed from intergranular to transgranular cleavage fracture. Further addition of Al resulted in the discontinuous growth of Ni2MnAl precipitates in the alloy containing 4.2 wt.% Al and fracture occurred by void growth and coalescence, i.e. by ductile dimple rupture. The transition of the fracture behaviour of the Fe-Mn-Ni-Al alloys is discussed in relation to the conversion of the precipitates and their discontinuous precipitation behaviour at PAGBs.

  19. Mn-Cr systematics in primitive meteorites: Insights from mineral separation and partial dissolution

    NASA Astrophysics Data System (ADS)

    Göpel, Christa; Birck, Jean-Louis; Galy, Albert; Barrat, Jean-Alix; Zanda, Brigitte

    2015-05-01

    Cr isotopic compositions have been measured on carbonaceous chondrites (CC): Tafassasset, Paris, Niger I, NWA 5958, NWA 8157 and Jbilet Winselwan. In bulk samples, the 54Cr/52Cr ratios (expressed as ε54Cr) range from 0.93 to 1.58 ε units. These values are in agreement with values characteristic for distinct petrologic types. Despite this 54Cr heterogeneity, the variability in the 53Cr/52Cr ratios (expressed as ε53Cr) of 0.2 ε units and the Mn/Cr ratios is consistent with the previous finding of an isochron in the Mn-Cr evolution diagram. The Mn/Cr ratio in CC corresponds to variable abundances of high-T condensate formed and separated at the beginning of the solar system, thus the canonical 53Mn/55Mn ratio can be defined. Based on a consistent chronology for U-Pb and Mn-Cr between the earliest objects formed in the solar nebula and the D'Orbigny angrite we define a canonical 53Mn/55Mn ratio and ε53Cri of 6.8 × 10-6 and -0.177, respectively. The internal Mn/Cr systematics in Tafassasset and Paris were studied by two approaches: leaching technique and mineral separation. Despite variable ε54Cr values (up to >30 ε) linear co-variations were found between ε53Cr and Mn/Cr ratio. The mineral separates as well as the leachates of Tafassasset fall on a common isochron indicating that (1) cooling of the Tafassasset's parent body occurred at 4563.5 ± 0.25 Ma, and that (2) 54Cr is decoupled from the other isotopes even though temperatures >900 °C have been reached during metamorphism. In the case of Paris, the leachates form an alignment with a 53Mn/55Mn ratio higher than the canonical value. This alignment is not an isochron but rather a mixing line. Based on leachates from various CM and CI, we propose the occurrence of three distinct Cr reservoirs in meteoritic material: PURE54, HIGH53 and LOW53 characterized by a ε53Cr and ε54Cr of 0 and 25,000, -2.17 and 8, and 0.5 and -151, respectively. PURE54 has already been described and is carried by highly refractory

  20. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting.

    PubMed

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng-Chang; Wang, Di-Yan; Yang, Jiang; Hwang, Bing-Joe; Dai, Hongjie

    2015-10-01

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2 O3 -blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2 O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2 O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm(-2) at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. The non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells. PMID:26307213

  1. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting

    DOE PAGESBeta

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng -Chang; Wang, Di -Yan; Yang, Jiang; et al

    2015-08-24

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2O3-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20more » mA cm–2 at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. Thus, the non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.« less

  2. Ferromagnetic interactions and martensitic transformation in Fe doped Ni-Mn-In shape memory alloys

    SciTech Connect

    Lobo, D. N.; Priolkar, K. R.; Emura, S.; Nigam, A. K.

    2014-11-14

    The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni{sub 2}MnIn{sub 1−x}Fe{sub x} (0 ≤ x ≤ 0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni{sub 2}Mn{sub 1.5}In{sub 1−y}Fe{sub y} and Ni{sub 2}Mn{sub 1.6}In{sub 1−y}Fe{sub y} increases for lower Fe concentrations (y ≤ 0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni{sub 2}MnIn{sub 1−x}Fe{sub x} at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.

  3. Strain mediated coupling in magnetron sputtered multiferroic PZT/Ni-Mn-In/Si thin film heterostructure

    SciTech Connect

    Singh, Kirandeep; Kaur, Davinder; Singh, Sushil Kumar

    2014-09-21

    The strain mediated electrical and magnetic properties were investigated in PZT/Ni-Mn-In heterostructure deposited on Si (100) by dc/rf magnetron sputtering. X-ray diffraction pattern revealed that (220) orientation of Ni-Mn-In facilitate the (110) oriented tertragonal phase growth of PZT layer in PZT/Ni-Mn-In heterostructure. A distinctive peak in dielectric constant versus temperature plots around martensitic phase transformation temperature of Ni-Mn-In showed a strain mediated coupling between Ni-Mn-In and PZT layers. The ferroelectric measurement taken at different temperatures exhibits a well saturated and temperature dependent P-E loops with a highest value of P{sub sat}~55 μC/cm² obtained during martensite-austenite transition temperature region of Ni-Mn-In. The stress induced by Ni-Mn-In layer on upper PZT film due to structural transformation from martensite to austenite resulted in temperature modulated Tunability of PZT/Ni-Mn-In heterostructure. A tunability of 42% was achieved at 290 K (structural transition region of Ni-Mn-In) in these heterostructures. I-V measurements taken at different temperatures indicated that ohmic conduction was the main conduction mechanism over a large electric field range in these heterostructures. Magnetic measurement revealed that heterostructure was ferromagnetic at room temperature with a saturation magnetization of ~123 emu/cm³. Such multiferroic heterostructures exhibits promising applications in various microelectromechanical systems.

  4. Characteristics of radiation porosity and structural phase state of reactor austenitic 07C-16Cr-19Ni-2Mo-2Mn-Ti-Si-V-P-B Steel after neutron irradiation at a temperature of 440-600°C to damaging doses of 36-94 dpa

    NASA Astrophysics Data System (ADS)

    Portnykh, I. A.; Panchenko, V. L.

    2016-06-01

    The phase composition and the characteristics of vacancy voids in cold-worked steel 07C-16Cr-19Ni-2Mo-2Mn-Ti-Si-V-P-B (CW EK164-ID) after neutron irradiation at damaging doses of 36-94 dpa and temperatures of 440-600°C are investigated. In the entire range of damaging doses and temperatures, voids with different sizes are observed in the material. The maximum void size increases with irradiation temperature up to ~550°C, whereas their concentration decreases. At higher irradiation temperatures, almost no coarse voids are observed. The concentration of fine voids (to 10 nm in size) sharply increases with temperature from 440 to 480°C. Further increases in the temperature do not result in the noticeable concentration growth. In the irradiation temperature range of 440-515°C, second phases precipitate ( G phase, γ' phase, and complex fcc carbides). At higher irradiation temperatures, there are Laves-phase particles, fine second carbides of the MC type, and needle shape precipitates identified as phosphides in the material.

  5. Synthesis and Characterization of Poly-phase Waste Form: Gd{sub 3}Fe{sub 5}O{sub 12}+(Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4}

    SciTech Connect

    Chae, S.C.; Jang, Y.N.; Bae, I.K.; Ryu, K.W.

    2006-07-01

    The synthesis of poly-phase waste form, which is an immobilization matrix for the HLW, was performed with the mixed composition of garnet and spinel (Gd{sub 3}Fe{sub 5}O{sub 12}+(Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4}) at temperatures in the range of 1200 deg. C to 1400 deg. C. The phases synthesized from all stoichiometric compositions were garnet, perovskite, and spinel. Especially, garnet was synthesized only in the composition of the highest content of Fe(y=0.9), whereas it was not synthesized in other compositions. This result indicated that the content of Fe was closely related to the formation of garnet. The composition of garnet revealed that the content of Gd was exceeded and that of Fe was depleted. Preferential distribution of elements in the phases can be attributed to the nonstoichiometric composition of garnet. (authors)

  6. Influence of the presence of pre-existing thermal [var epsilon]-martensite on the formation of stress-induced [var epsilon]-martensite and on the shape memory effect of a Fe-Mn-Cr-Si-Ni shape memory alloy

    SciTech Connect

    Federzoni, L.; Guenin, G. )

    1994-07-01

    At present, many investigations are done on Fe-Mn-based shape memory alloys because of their particularly good one-way type shape memory effect and their low cost. With addition of Cr and Ni, it is possible to reach a good corrosion resistance, which confers to this type of alloys a commercial significance. The shape memory effect is associated with the formation of stress-induced [var epsilon]-martensite by deformation of an austenitic ([gamma]) sample. The reversion by heating of the [var epsilon]-martensite provides the shape memory effect. It is generally admitted that the presence of thermal [var epsilon]-martensite before deformation has a negative influence on the formation of the stress-induced martensite and on the shape memory effect. The authors' purpose is to evaluate the real influence of the pre-existing thermal [var epsilon]-martensite on the formation of the stress-induced [var epsilon]-martensite, its recovery and on the shape memory effect.

  7. Long afterglow properties of Zn2GeO4:Mn2+, Cr3+ phosphor

    NASA Astrophysics Data System (ADS)

    Cong, Yan; He, Yangyang; Dong, Bin; Xiao, Yu; Wang, Limei

    2015-04-01

    Zn2GeO4:Mn2+, Cr3+ phosphors were prepared by conventional solid state reaction and the photoluminescence properties were investigated. The Mn2+ activated Zn2GeO4 phosphors exhibited green emission at 533 nm due to the 4T1(4G) → 6A1(6S) transition of Mn2+ ions. With Cr3+ co-doping in Zn2GeO4 host, long afterglow characteristics were found from the same transition of Mn2+. The TL results revealed the presence of same traps in the phosphor, and the doping of Cr3+ ions deepened the VGe traps. The native defect VGe as a hole traps is responsible for the long afterglow emission in Zn2GeO4:Mn2+, Cr3+ phosphor. The possible mechanism of this phosphor has also been discussed.

  8. Development and High Temperature Property Evaluation of Ni-Co-Cr-Al Composite Electroforms

    NASA Astrophysics Data System (ADS)

    Srivastava, Meenu; Siju; Balaraju, J. N.; Ravisankar, B.

    2015-05-01

    Ni-Co-Cr-Al composite electroforms were developed with cobalt content of 10 and 40 wt.%. Cr and Al nano-particles were suspended in sulphamate electrolyte and co-deposited in the Ni-Co matrices. The surface morphology was investigated using field emission scanning electron microscope and the composition analyzed by energy-dispersive x-ray analysis. The oxidation resistance of the electroforms was studied from 600 to 1000 °C. The weight gain of Ni-10 wt.%Co-Cr-Al was less (better oxidation resistance) compared to Ni-Cr-Al and Ni-40 wt.%Co-Cr-Al. The x-ray diffraction studies revealed that the oxidation product formed on the surface of Ni-Cr-Al and Ni-10 wt.%Co-Cr-Al consisted of NiO and Al2O3, while Ni-40 wt.%Co-Cr-Al comprised oxides such as NiCo2O4, CrO3, CoO, NiO, and Al2O3. The hot corrosion behavior was investigated in 75%Na2SO4 + 25%NaCl environment at 800 °C. It was found that the hot corrosion resistance of the composite coating improved with increase in cobalt content. The probable composition suitable for high-temperature applications was found to be Ni-10 wt.%Co-Cr-Al.

  9. Role of oxygen diffusion at Ni/Cr2O3 interface in intergranular oxidation of Ni-Cr alloy

    NASA Astrophysics Data System (ADS)

    Medasani, Bharat; Sushko, Maria; Schreiber, Daniel; Rosso, Kevin; Bruemmer, Stephen

    Certain Ni-Cr alloys used in nuclear systems experience intergranular oxidation and stress corrosion cracking when exposed to high-temperature water leading to their degradation and unexpected failure. To develop a mechanistic understanding of grain boundary oxidation processes, we proposed a mesoscale metal alloy oxidation model that combines quantum Density Functional Theory (DFT) with mesoscopic Poisson-Nernst-Planck/classical DFT. This framework encompasses the chemical specificity of elementary diffusion processes and mesoscale reactive dynamics, and allows modeling oxidation processes on experimentally relevant length scales from first principles. As a proof of concept, a preliminary model was previously employed that limited oxygen diffusion pathways to those through the oxide phase and did not allow oxygen diffusion in the alloy or across oxide/alloy interfaces. In this work, we expand the model to include oxygen diffusion pathways along Ni/Cr2O3 interfaces and demonstrate the increasing importance of such pathways for intergranular oxidation of Ni-Cr alloys with high Cr content. This work is supported by the U.S. Dept. of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. Simulations are performed using PNNL Institutional Computing facility.

  10. Film Thickness Influences on the Thermoelectric Properties of NiCr/NiSi Thin Film Thermocouples

    NASA Astrophysics Data System (ADS)

    Chen, Y. Z.; Jiang, H. C.; Zhang, W. L.; Liu, X. Z.; Jiang, S. W.

    2013-06-01

    NiCr/NiSi thin film thermocouples (TFTCs) with a multi-layer structure were fabricated on Ni-based superalloy substrates (95 mm × 35 mm × 2 mm) by magnetron sputtering and electron beam evaporation. The five-layer structure is composed of NiCrAlY buffer layer (2 μm), thermally grown Al2O3 bond layer (200 nm), Al2O3 insulating layer (10 μm), NiCr/NiSi TFTCs (1 μm), and Al2O3 protective layer (500 nm). Influences of thermocouple layer thickness on thermoelectric properties were investigated. Seebeck coefficient of the samples with the increase in thermocouple layer thickness from 0.5 μm to 1 μm increased from 27.8 μV/°C to 33.8 μV/°C, but exhibited almost no change with further increase in thermocouple layer thickness from 1 μm to 2 μm. Dependence on temperature of the thermal electromotive force of the samples almost followed standard thermocouple characteristic curves when the thickness of the thermocouple layer was 1 μm and 2 μm. Sensitive coefficient K of the samples increased greatly with the increase in thickness of the thermocouple layer from 0.5 μm to 1 μm, but decreased insignificantly with the increase in thermocouple layer thickness from 1 μm to 2 μm, and continuously decreased with the increase in temperature. The sensitive coefficient and the stability of NiCr/NiSi TFTCs were both improved after annealing at 600°C.

  11. NiAl(110)/Cr(110) interface: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Liu, W.; Li, J. C.; Zheng, W. T.; Jiang, Q.

    2006-05-01

    The optimal geometries, thermodynamic properties, and electronic structures of NiAl(110)/Cr(110) interface are studied using a first-principle density functional plane-wave ultrasoft pseudopotential method. Surface energies of different NiAl surfaces are compared with those obtained based on the classical broken-bond rule. Simulation results indicate that the structure of Ni and Al placed in the hollow sites of Cr atoms at the interface is more thermodynamically stable, and the NiCr bonding is dominated by 3d electrons of Ni and Cr. It is found that NiAl(110)/Cr(110) alloying could lower brittleness of NiAl compounds. With simulated values of adhesion work and interface energy for NiAl(110)/Cr(110) system, its mechanical and thermodynamic properties are also discussed.

  12. Eutectic equilibria in the quaternary system Fe-Cr-Mn-C

    NASA Technical Reports Server (NTRS)

    Nowotny, H.; Wayne, S.; Schuster, J. C.

    1982-01-01

    The constitution of the quaternary system, Fe-Cr-Mn-C and to a lesser extent of the quinary system, Fe-Cr-Mn-Al-C were examined for in situ composite alloy candidates. Multivariant eutectic compositions were determined from phase equilibria studies wherein M7C3 carbides (approximately 30% by volume) formed from the melt within gamma iron. An extended field of the hexagonal carbide, (Cr, Fe, Mn)7 C3, was found without undergoing transformation to the orthorhombic structure. Increasing stability for this carbide was found for higher ratios of Cr/Fe(+) Cr + Mn. Aluminum additions promoted a ferritic matrix while manganese favored the desired gamma austenitic matrix. In coexistence with the matrix phase, chromium enters preferentially the carbide phase while manganese distributes equally between the gamma matrix and the M7C3 carbide. The composition and lattice parameters of the carbide and matrix phases were determined to establish their respective stabilities.

  13. Ordering reactions in an Ni-25Mo-8Cr alloy

    SciTech Connect

    Kumar, M.; Vasudevan, V.K.

    1996-04-01

    The transformations from short- to long-range order in Haynes{reg_sign} Alloy 242, a nominal Ni-25Mo-8Cr (in wt%) alloy, during isothermal aging at temperatures between 550 and 750 C are reported using microhardness measurements, and optical and transmission electron microscopy. Aging below the critical transformation temperature ({approximately} 775 C) led to considerable hardening; this hardening was associated with the formation of a very high volume fraction of Ni{sub 2} (Mo,Cr) domains/precipitates. The transformation from short- to long-range order was observed to proceed by a mechanism of continuous ordering at temperatures {le} 700 C, whereas at temperatures (750 C) close to the critical temperature a first order nucleation and growth mechanism appeared to be operative. The sequence of transformations are correlated with the associated diffraction effects and discussed in terms of theoretical formulations and experimental observations of other studies.

  14. Precipitation Strengthening in Al-Ni-Mn Alloys

    NASA Astrophysics Data System (ADS)

    Fan, Yangyang; Huang, Kai; Makhlouf, Makhlouf M.

    2015-12-01

    Precipitation hardening of eutectic and hypoeutectic Al-Ni alloys by 2 to 4 wt pct. manganese is investigated with focus on the effect of the alloys' chemical composition and solidification cooling rate on microstructure and tensile strength. Within the context of the investigation, mathematical equations based on the Orowan Looping strengthening mechanism were used to calculate the strengthening increment contributed by each of the phases present in the aged alloy. The calculations agree well with measured values and suggest that the larger part of the alloy's yield strength is due to the Al3Ni eutectic phase, this is closely followed by contribution from the Al6Mn particles, which precipitate predominantly at grain boundaries.

  15. Directionally solidified pseudo-binary eutectics of Ni-Cr-(Hf, Zr)

    NASA Technical Reports Server (NTRS)

    Kim, Y. G.; Ashbrook, R. L.

    1975-01-01

    A pseudo-binary eutectic, in which the intermetallic Ni7Hf2 reinforces the Ni-Cr solid solution phase, was previously predicted in the Ni-Cr-Hf system by a computer analysis. The experimental determination of pseudo binary eutectic compositions and the directional solidification of the Ni-Cr-Hf, Zr, and Ni-Cr-Zr eutectic alloys are discussed. To determine unknown eutectics, chemical analyses were made of material bled from near eutectic ingots during incipient melting. Nominal compositions in weight percent of Ni-18.6Cr-24.0HF, Ni19.6Cr-12.8Zr-2.8Hf, and Ni-19.2Cr-14.8Zr formed aligned pseudo-binary eutectic structures. The melting points were about 1270 C. The reinforcing intermetallic phases were identified as noncubic (Ni,Cr)7Hf2 and (Ni,Cr)7(Hf,Zr)2, and face centered cubic (Ni,Cr)5Zr. The volume fraction of the reinforcing phases were about 0.5.

  16. Precipitation in 9Ni-12Cr-2Cu maraging steels

    SciTech Connect

    Stiller, K.; Haettestrand, M.; Danoix, F.

    1998-11-02

    Two maraging steels with the compositions 9Ni-12Cr-2Cu-4Mo (wt%) and 9Ni-12Cr-2Cu and with small additions of Al and Ti were investigated using atom probe field ion microscopy. Tomographic atom probe investigations were performed to clarify the spatial distribution of elements in and close to the precipitates. Materials heat treated at 475 C for 5, 25 min, 1, 2, 4 and 400 h were analyzed. Precipitates in the Mo-rich material were observed already after 5 min of aging, while in the material without MO, precipitation started later. In both materials precipitation begins with the formation of Cu-rich particles which work as nucleation sites for a Ni-rich phase of type Ni{sub 3}(Ti,Al). A Mo-rich phase was detected in the Mo-rich steel after 2 h of aging. The distribution of alloying elements in the precipitates, their role in the precipitation process, and the mechanism of hardening in the two materials are discussed.

  17. Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Bojack, A.; Zhao, L.; Morris, P. F.; Sietsma, J.

    2016-05-01

    The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stages. This is probably due to inhomogeneous distribution of the austenite-stabilizing elements Ni and Mn, resulting from their slow diffusion from martensite into austenite and carbide and nitride dissolution during the second, higher temperature, stage. A better homogenization of the material causes an increase in the transformation temperatures for the martensite-to-austenite transformation and a lower retained austenite fraction with less variability after tempering. Furthermore, the martensite-to-austenite transformation was found to be incomplete at the target temperature of 1223 K (950 °C), which is influenced by the previous austenitization treatment and the heating rate. The activation energy for martensite-to-austenite transformation was determined by a modified Kissinger equation to be approximately 400 and 500 kJ/mol for the first and the second stages of transformation, respectively. Both values are much higher than the activation energy found during isothermal treatment in a previous study and are believed to be effective activation energies comprising the activation energies of both mechanisms involved, i.e., nucleation and growth.

  18. Microstructure of the Native Oxide Layer on Ni and Cr-doped Ni Nanoparticles

    SciTech Connect

    Wang, Chong M.; Baer, Donald R.; Bruemmer, Stephen M.; Engelhard, Mark H.; Bowden, Mark E.; Sundararajan, J. A.; Qiang, You

    2011-10-01

    Metallic or alloy nanoparticles exposed to air at room temperature will be instantaneously oxidized and covered by an oxide layer. However, for most cases, the true structural nature of the oxide layer formed at this stage is hard to determine. In this paper, we report the structure, morphology, and electronic structure (the density of state of both valence and conduction bands measured by a combination of XPS and EELS) of pure Ni and Cr-doped Ni nanoparticles synthesized using a cluster deposition process. Structural characterization carried out at the atomic level using aberration corrected high resolution transmission electron microscopy (HRTEM) in combination with electron and x-ray diffractions reveals that both pure Ni and Cr-doped Ni particles exposed to air at room temperature similarly possesses a core-shell structure of metal core covered by an oxide layer of typically 1.6 nm in thickness. There exists a critical size of ~ 6 nm, below which the particle is fully oxidized. The oxide particle corresponds to the rock-salt structured NiO and is faceted on the (001) planes. XPS of O-1s shows a strong peak that is attributed to (OH)-, which in combination with the atomic level HRTEM imaging indicates that the very top layer of the oxide is hydrolyzed as Ni(OH)2. Chemical composition analysis using EDS, EELS, and XPS indicates that the Cr dopant at the level of ~ 5at% forms solid solution with the Ni lattice. The Cr shows no segregation on the surface or preferential oxidation during the initial oxidation.

  19. The erosion-oxidation behavior of HVOF Cr{sub 3}C{sub 2}-NiCr cermet coating

    SciTech Connect

    Wang, B.Q.; Luer, K.

    1994-12-31

    DenSys DS-200 coating is a proprietary HVOF Cr{sub 3}C{sub 2}-NiCr cermet coating used in elevated temperature service environments including fluidized bed boilers, coal-fired boilers and municipal waste incinerators. The elevated temperature erosion-corrosion (oxidation) behavior of this HVOF Cr{sub 3}C{sub 2}-NiCr coating was investigated using a range of test temperatures, impact angles, erodents, and particle velocities. The erosion-corrosion behavior of HVOF Cr{sub 3}C{sub 2}-NiCr coatings was compared with 1018 steel and other thermal-spray coatings including FeCrSiB (Armacor M), Ni-base, Cr{sub 2}O{sub 3}-6SiO{sub 2}-4Al{sub 2}O{sub 3} (Rokide C), Cr{sub 2}O{sub 3}-12SiO{sub 2}-2Al{sub 2}O{sub 3}-4MgO (Rokide MBC), and WC-NiCrCo (SMI 712). It was found that the erosion-oxidation resistance of HVOF Cr{sub 3}C{sub 2}-NiCr coating was higher than 1018 steel and other coatings at both impact angles 30{degree} and 90{degree}. The erosion-oxidation behavior of coatings was well related to their morphology. The high erosion-oxidation resistance of the HVOF Cr{sub 3}C{sub 2}-NiCr coating was attributed to its low porosity, fine grain structure and homogeneous distribution of hard carbides/oxides which form a skeletal network within a ductile and corrosion-resistant metal binder.

  20. Ductile-brittle-ductile transition and grain boundary segregation of Mn and Ni in an Fe-6Mn-12Ni alloy

    SciTech Connect

    Heo, N.H.

    1996-05-15

    Recently, Heo and Lee reported a ductile-brittle-ductile (DBD) transition in an Fe-8Mn-7Ni ternary alloy, which was caused by manganese segregation to the grain boundaries and its desegregation into the matrix. More recently Heo theoretically analyzed the nonequilibrium segregation behaviors of the elements in the Fe-8Mn-7Ni alloy. The aim of the present study is to investigate whether other Fe-6Mn-12Ni ternary alloy also shows the ductile-brittle-ductile transition, and is additionally to ascertain whether calculated results are consistent with experimental data. The study encompasses experimental procedures and a modeling based on the previous research. A general discussion will show that such an approach allows a comprehensive understanding of the ductile-brittle-ductile transition in the Fe-Mn-Ni ternary alloys.

  1. The electrodeposition of FeCrNi stainless steel: microstructural changes induced by anode reactions.

    PubMed

    Hasegawa, Madoka; Yoon, Songhak; Guillonneau, Gaylord; Zhang, Yucheng; Frantz, Cédric; Niederberger, Christoph; Weidenkaff, Anke; Michler, Johann; Philippe, Laetitia

    2014-12-21

    The FeCrNi alloy, whose composition is close to that of stainless steel 304, was prepared by electrodeposition and characterized. Nanocrystalline FeCrNi (nc-FeCrNi) was obtained by employing a double-compartment cell where the anode is separated from the cathode compartment, while amorphous FeCrNi (a-FeCrNi) was deposited in a conventional single electrochemical cell. The carbon content of nc-FeCrNi was found to be significantly lower than that of a-FeCrNi, suggesting that carbon inclusion is responsible for the change in the microstructure. The major source of carbon is associated with the reaction compounds at the anode electrode, presumably decomposed glycine. Crystal structure analysis by XRD and TEM revealed that the as-deposited nc-FeCrNi deposits consist of α-Fe which transforms to γ-Fe upon thermal annealing. Nanoindentation tests showed that nc-FeCrNi exhibits higher hardness than a-FeCrNi, which is consistent with the inverse Hall-Petch behavior. PMID:25367332

  2. Hot corrosion of Co-Cr, Co-Cr-Al, and Ni-Cr alloys in the temperature range of 700-750 deg C

    NASA Technical Reports Server (NTRS)

    Chiang, K. T.; Meier, G. H.

    1980-01-01

    The effect of SO3 pressure in the gas phase on the Na2SO4 induced hot corrosion of Co-Cr, Ni-Cr, and Co-Cr-Al alloys was studied in the temperature range 700 to 750 C. The degradation of the Co-Cr and Ni-Cr alloys was found to be associated with the formation of liquid mixed sulfates (CoSO4-Na2SO4 or NiSO4-Na2SO4) which provided a selective dissolution of the Co or Ni and a subsequent sulfidation oxidation mode of attack which prevented the maintenance of a protective Cr2O3 film. A clear mechanism was not developed for the degradation of Co-Cr-Al alloys. A pitting corrosion morphology was induced by a number of different mechanisms.

  3. Oxidation Behavior and Electrical Properties of NiO- and Cr2O3- Forming Alloys for Solid Oxide Fuel Cell Interconnects.

    SciTech Connect

    Brady, Michael P; Pint, Bruce A; Lu, Z G; Zhu, Jiahong; Milliken, C; kreidler, E; Miller, Leslie S; Armstrong, Timothy R.; Walker, Larry R

    2006-01-01

    The goal of this paper was to determine if NiO-forming alloys are a viable alternative to Cr{sub 2}O{sub 3}-forming alloys for solid-oxide fuel-cell (SOFC) metallic interconnects. The oxide-scale growth kinetics and electrical properties of a series of Li- and Y{sub 2}O{sub 3}-alloyed, NiO-forming Ni-base alloys and La-, Mn-, and Ti-alloyed Fe-18Cr-9W and Fe-25Cr base ferritic Cr{sub 2}O{sub 3}-forming alloys were evaluated. The addition of Y{sub 2}O{sub 3} and Li reduced the NiO scale growth rate and increased its electrical conductivity. The area-specific-resistance (ASR) values were comparable to those of the best (lowest ASR) ferritic alloys examined. Oxidation of the ferritic alloys at 800 C in air and air+10% H{sub 2}O (water vapor) indicated that Mn additions resulted in faster oxidation kinetics/thicker oxide scales, but also lower oxide scale ASRs. Relative in-cell performance in model SOFC stacks operated at 850 C indicated a 60-80% reduction in ASR by Ni+Y{sub 2}O{sub 3}, Ni+Y{sub 2}O{sub 3}, Li, and Fe-25Cr+La,Mn,Ti interconnects over those made from a baseline, commercial Cr{sub 2}O{sub 3}-forming alloy. Collectively, these results indicate that NiO-forming alloys show potential for use as metallic interconnects.

  4. Studies on the Sliding Wear Performance of Plasma Spray Ni-20Cr and Ni3Al Coatings

    NASA Astrophysics Data System (ADS)

    Kaur, Maninder; Singh, Harpreet; Singh, Balraj; Singh, Bhupinder

    2010-01-01

    Two metallic powders namely Ni-20Cr and Ni3Al were coated on AISI 309 SS steel by shrouded plasma spray process. The wear behavior of the bare, Ni-20Cr and Ni3Al-coated AISI 309 SS steel was investigated according to ASTM Standard G99-03 on a Pin-on-Disc Wear Test Rig. The wear tests were carried out at normal loads of 30 and 50 N with a sliding velocity of 1 m/s. Cumulative wear rate and coefficient of friction (μ) were calculated for all the cases. The worn-out surfaces were then examined by scanning electron microscopy analysis. Both the as-sprayed coatings exhibited typical splat morphology. The XRD analysis indicated the formation of Ni phase for the Ni-20Cr coating and Ni3Al phase for the Ni3Al coating. It has been concluded that the plasma-sprayed Ni-20Cr and Ni3Al coatings can be useful to reduce the wear rate of AISI 309 SS steel. The coatings were found to be adherent to the substrate steel during the wear tests. The plasma-sprayed Ni3Al coating has been recommended as a better choice to reduce the wear of AISI 309 SS steel, in comparison with the Ni-20Cr coating.

  5. Magnetism of NiMn2O4-Fe3O4 spinel interfaces

    SciTech Connect

    Arenholz, Elke; Nelson-Cheeseman, B. B.; Chopdekar, R. V.; Bettinger, J. S.; Arenholz, E.; Suzuki, Y.

    2007-09-13

    We investigate the magnetic properties of the isostructural spinel-spinel interface of NiMn{sub 2}O{sub 4}(NMO)-Fe{sub 3}O{sub 4}. Although the magnetic transition temperature of the NMO film is preserved, both bulk and interface sensitive measurements demonstrate that the interface exhibits strong interfacial magnetic coupling up to room temperature. While NMO thin films have a ferrimagnetic transition temperature of 60 K, both NiFe{sub 2}O{sub 4} and MnFe{sub 2}O{sub 4} are ferrimagnetic at room temperature. Our experimental results suggest that these magnetic properties arise from a thin interdiffused region of (Fe,Mn,Ni){sub 3}O{sub 4} at the interface, leading to Mn and Ni magnetic properties similar to those of MnFe{sub 2}O{sub 4} and NiFe{sub 2}O{sub 4}.

  6. Influence of the chemical composition of rapidly quenched amorphous alloys (Ni, Fe, Cr)-B-Si on its crystallization process

    NASA Astrophysics Data System (ADS)

    Elmanov, G.; Dzhumaev, P.; Ivanitskaya, E.; Skrytnyi, V.; Ruslanov, A.

    2016-04-01

    This paper presents results of research of the structure and phase transformations during the multistage crystallization of the metallic glasses with the compositions Ni71,5Cr6,8Fe2,7B11,9Si7,1 and Ni63,4Cr7,4Fe4,3Mn0,8B15,6Si8,5 labeled as AWS BNi-2 according to American Welding Society. Differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX) were used as experimental research methods. The influence of the alloys chemical composition (boron, manganese and iron) on the temperatures and the exothermic heat effects of phase transformations, as well as on the phase composition of alloys at three stages of crystallization was analyzed. We present a thermodynamic explanation of the observed heat effects. It has been shown that manganese has the main influence on the phase transformations temperatures and heat effects in these two alloys. It is also assumed that at the final crystallization stage simultaneously with the formation of phases Ni3B and β1-Ni3Si should occur the nucleation of borides of CrB type with high Cr and low Si content.

  7. Strain hardening mechanisms in a Ni-Mo-Cr alloy

    SciTech Connect

    Dymek, S. ); Dollar, M. ); Klarstrom, D.L. )

    1991-01-01

    HAYNES 242 alloy has been recently developed for gas turbine components applications. This age-hardenable alloy, consisting essentially of Ni-25%Mo-8%Cr, utilizes a long-range-ordering reaction to form uniformly sized and distributed, extremely small (on the order of 10nm), ordered particles. Excellent strength and ductility at elevated temperatures, low thermal expansion characteristics and good oxidation resistance of Haynes 242 alloy has encouraged a number of studies designed to characterize its properties. What is lacking is an attempt to understand the fundamentals of the deformation and strengthening mechanisms in this alloy. This on-going research has been undertaken to explore deformation mechanisms in unaged and aged Haynes 242 alloy. The emphasis has been put on the effects of initial precipitation structure on the development of deformation structure and how it controls selected mechanical properties. This paper presents selected results and reports a change in the deformation mode from crystallographic glide in an unaged alloy into twinning in the presence of ordered particles. Deformation twinning in Ni-Mo and Ni-Mo-Cr alloys was reported earlier but was not discussed in detail. This research sheds light on possible origins of particle-induced twinning in alloys strengthened by small ordered particles.

  8. Preparation, structural and magnetic characterization of DyCrMnO{sub 5}

    SciTech Connect

    Martinez-Lope, M.J.; Retuerto, M. Garcia-Hernandez, M.; Alonso, J.A.

    2009-03-15

    The title compound has been first synthesized by a citrate technique followed by thermal treatments under moderate oxygen pressure conditions, and characterized by X-ray and neutron powder diffraction (NPD) and magnetization measurements. The crystal structure of DyCrMnO{sub 5} has been refined from NPD data in the space group Pbam; a=7.2617(6) A, b=8.5161(6) A, and c=5.7126(5) A at 295 K. This oxide is isostructural with RMn{sub 2}O{sub 5} oxides (R=rare earths) and it contains infinite chains of (Cr, Mn){sup 4+}O{sub 6} octahedra-sharing edges, linked together by (Mn, Cr){sup 3+}O{sub 5} pyramids and DyO{sub 8} units. The high degree of antisite disordering exhibited by DyCrMnO{sub 5} is noteworthy. The octahedral positions are occupied by roughly 50% of Mn and Cr cations, and the pyramidal groups contain two thirds of Mn and one third of Cr cations. We assume that Mn and Cr cations at the octahedral positions exhibit a tetravalent oxidation state, whereas the metals at the pyramidal positions are trivalent, in order to preserve the electroneutrality of this oxide. The susceptibility vs temperature curve of DyCrMnO{sub 5} does not suggest the establishment of a long-range magnetic structure even at low temperatures; the NPD technique does not provide any signal of magnetic ordering, since the reflections do not show any magnetic contribution. - Graphical abstract: DyCrMnO{sub 5} is isostructural with DyMn{sub 2}O{sub 5}, belonging to the Pbam space group. The crystal structure contains infinite chains of edge-sharing Mn{sup 4+}O{sub 6} octahedra, interconnected by dimer units of Cr{sup 3+}O{sub 5} square pyramids. The low-temperature neutron powder diffraction (NPD) patterns do not show any magnetic contribution, indicating that a full long-range magnetic ordering is not established down to low temperature, although the Dy{sup 3+} magnetic moments are susceptible to be polarized by an external magnetic field at the lowest temperature of 5 K.

  9. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix.

    PubMed

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively. PMID:26750659

  10. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix

    NASA Astrophysics Data System (ADS)

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively.

  11. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix

    PubMed Central

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively. PMID:26750659

  12. Characterizations and hot corrosion resistance of Cr3C2-NiCr coating on Ni-base superalloys in an aggressive environment

    NASA Astrophysics Data System (ADS)

    Sidhu, T. S.; Prakash, S.; Agrawal, R. D.

    2006-12-01

    In the current study, Cr3C2-NiCr coating was deposited on the Ni-base superalloys by using high velocity oxyfuel (HVOF) process for high temperature corrosive environment applications. Optical microscopy (OM), x-ray diffraction (XRD), scanning electron microscopy/energy-dispersive analysis (SEM/EDAX), microhardness tester, and electro probe microanalyzer (EMPA) techniques were used to characterize the coating with regard to coating thickness, porosity, microhardness, and microstructure. The thermogravimetric technique was used to establish kinetics of corrosion. The hot corrosion behaviors of the bare and Cr3C2-NiCr coated superalloys were studied after exposure to aggressive environment of Na2SO4-60% V2O5 salt mixture at 900 °C under cyclic conditions. The structure of the as-sprayed Cr3C2-NiCr coating mainly consisted of γ-nickel solid solution along with minor phases of Cr7C3 and Cr2O3. Coating has porosity less than 1.5% and microhardness in the range of 850-900 Hv (Vickers hardness). Some inclusions, unmelted and semimelted powder particles were observed in the structure of the coatings. The Cr3C2-NiCr coating has imparted necessary resistance to hot corrosion, which has been attributed to the formation of oxides of nickel and chromium, and spinel of nickel-chromium.

  13. A sulfur segregation study of PWA 1480, NiCrAl, and NiAl alloys

    NASA Technical Reports Server (NTRS)

    Jayne, D. T.; Smialek, J. L.

    1993-01-01

    Some nickel based superalloys show reduced oxidation resistance from the lack of an adherent oxide layer during high temperature cyclic oxidation. The segregation of sulfur to the oxide-metal interface is believed to effect oxide adhesion, since low sulfur alloys exhibit enhanced adhesion. X ray Photoelectron Spectroscopy (XPS) was combined with an in situ sample heater to measure sulfur segregation in NiCrAl, PWA 1480, and NiAl alloys. The polished samples with a 1.5 to 2.5 nm (native) oxide were heated from 650 to 1100 C with hold times up to 6 hr. The sulfur concentration was plotted as a function of temperature versus time at temperature. One NiCrAl sulfur study was performed on the same casting used by Browning to establish a base line between previous Auger Electron Spectroscopy (AES) results and the XPS results of this study. Sulfur surface segregation was similar for PWA 1480 and NiCrAl and reached a maximum of 30 at% at 800 to 850 C. Above 900 C the sulfur surface concentration decreased to about 3 at% at 1100 C. These results are contrasted to the minimal segregation observed for low sulfur hydrogen annealed materials which exhibit improved scale adhesion.

  14. Oxide Transformation in Cr-Mn-Prealloyed Sintered Steels: Thermodynamic and Kinetic Aspects

    NASA Astrophysics Data System (ADS)

    Hryha, Eduard; Nyborg, Lars

    2014-04-01

    The main obstacle for utilization of Cr and Mn as alloying elements in powder metallurgy is their high oxygen affinity leading to oxidation risk during powder manufacturing, handling, and especially during further consolidation. Despite the high purity of the commercially available Cr- and Mn-prealloyed iron powder grades, the risk of stable oxide formation during the sintering process remains. Thermodynamic and kinetic simulation of the oxide formation/transformation on the former powder surface during heating and sintering stages using thermodynamic modeling tools (Thermo-Calc and HSC Chemistry) was performed. Simulation is based on the results from the analysis of amount, morphology, and composition of the oxide phases inside the inter-particle necks in the specimens from interrupted sintering trials utilizing advanced analysis tools (HRSEM + EDX and XPS). The effect of the processing parameters, such as sintering atmosphere composition, temperature profile as well as graphite addition on the possible scenarios of oxide reduction/formation/transformation for Fe-Cr-Mn-C powder systems, was evaluated. Results indicate that oxide transformation occurs in accordance with the thermodynamic stability of oxides as follows: Fe2O3 → FeO → Fe2MnO4 → Cr2FeO4 → Cr2O3 → MnCr2O4 → MnO/MnSiO x → SiO2. Spinel MnCr2O4 was identified as the most stable oxide phase at applied sintering conditions up to 1393 K (1120 °C). Controlled conditions during the heating stage minimize the formation of stable oxide products and produce oxide-free sintered parts.

  15. Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys

    NASA Astrophysics Data System (ADS)

    Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Gajjar, P. N.; Bhatt, N. K.; Jani, A. R.

    2011-12-01

    The temperature dependent electrical transport properties viz. electrical resistivity and thermal conductivity of Ni10Cr90 and Co20Cr80 alloys are computed at various temperatures. The electrical resistivity has been calculated according to Faber-Ziman model combined with Ashcroft-Langreth partial structure factors. In the present work, to include the ion-electron interaction, we have used a well tested local model potential. For exchange-correlation effects, five different forms of local field correction functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used. The present results due to S function are in good agreement with the experimental data as compared to results obtained using other four functions. The S functions satisfy compressibility sum rule in long wave length limit more accurately as compared to T, IU and F functions, which may be responsible for better agreement of results, obtained using S function. Also, present result confirms the validity of present approach in determining the transport properties of alloys like Ni-Cr and Co-Cr.

  16. Hybrid Co-Cr/W-WC and Ni-W-Cr-B/W-WC Coating Systems

    NASA Astrophysics Data System (ADS)

    Vernhes, L.; Azzi, M.; Bousser, E.; Schmitt, T.; Lamarre, J. M.; Klemberg-Sapieha, J. E.

    2016-01-01

    The aim of this study was to investigate the effects of subsurface materials on the performance of a wear-resistant thin film. The mechanical, tribological, and corrosion properties were assessed for two hybrid coating systems: (1) W-WC thin film and a laser cladded Co-Cr interlayer applied to a 316 stainless steel substrate and (2) the same W-WC thin film and a spray-and-fused Ni-W-Cr-B interlayer applied to an Inconel® 718 substrate. They were then compared to the same systems without an interlayer. The microstructures were analyzed by XRD, EDS, and SEM. The hardness and surface load-carrying capacity of the coating systems were determined by micro- and macrohardness testing. Rockwell indentation was used to assess coating adhesion (CEN/TS 1071-8). Tribological properties were assessed with a reciprocating tribometer, and corrosion resistance was determined by potentiodynamic polarization and electrochemical impedance spectroscopy. The originality of this work lies in the finding that, except for the Inconel 718/Ni-W-Cr-B/W-WC system, the wear rate decreases with decreasing hardness of the subsurface materials carrying the thin film due to the decreasing contact pressure for a given load. Another novel finding is the stress-induced phase transformation of the Co-Cr interlayer, which occurs beneath the thin film under high load.

  17. Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys

    SciTech Connect

    Thakore, B. Y.; Khambholja, S. G.; Bhatt, N. K.; Jani, A. R.; Suthar, P. H.; Gajjar, P. N.

    2011-12-12

    The temperature dependent electrical transport properties viz. electrical resistivity and thermal conductivity of Ni{sub 10}Cr{sub 90} and Co{sub 20}Cr{sub 80} alloys are computed at various temperatures. The electrical resistivity has been calculated according to Faber-Ziman model combined with Ashcroft-Langreth partial structure factors. In the present work, to include the ion-electron interaction, we have used a well tested local model potential. For exchange-correlation effects, five different forms of local field correction functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used. The present results due to S function are in good agreement with the experimental data as compared to results obtained using other four functions. The S functions satisfy compressibility sum rule in long wave length limit more accurately as compared to T, IU and F functions, which may be responsible for better agreement of results, obtained using S function. Also, present result confirms the validity of present approach in determining the transport properties of alloys like Ni-Cr and Co-Cr.

  18. Magnetism of ordered and disordered Ni2MnAl full Heusler compounds

    NASA Astrophysics Data System (ADS)

    Simon, E.; Vida, J. Gy.; Khmelevskyi, S.; Szunyogh, L.

    2015-08-01

    Based on ab initio calculations and Monte Carlo simulations, we present a systematic study of the magnetic ground state and finite temperature magnetism of ordered and disordered Ni2MnAl full Heusler compounds. By increasing the degree of the long-range chemical disorder between the Mn and Al sublattices, the magnetic order progressively changes from the ferromagnetic state in the ordered L 21 phase toward a fully compensated antiferromagnetic state in the disordered B 2 phase and we also conclude that the Ni atoms exhibit induced moments. We determine the Mn-Mn interactions by using the magnetic force theorem and find dominating, but rather weak ferromagnetic couplings in the ordered L 21 phase. We used a recently proposed renormalization technique to include the weak Ni moments into the spin model, which indeed remarkably increased the nearest-neighbor Mn-Mn interaction. In accordance with the total energy calculations, in the disordered compounds, strong antiferromagnetic site-antisite Mn-Mn interactions appear. Determining the spin-spin correlation functions from Monte Carlo simulations, we conclude that above the transition temperature, short-range antiferromagnetic correlations prevail between the Mn atoms. In view of the potential application of disordered Ni2MnAl as a room temperature antiferromagnet, we calculate the magnetic anisotropy energies of tetragonally distorted samples in the B 2 phase and find that they are smaller by two orders in magnitude than in the frustrated antiferromagnet IrMn3.

  19. Leaching of Mn, Co, and Ni from manganese nodules using an anaerobic bioleaching method.

    PubMed

    Lee, E Y; Noh, S; Cho, K; Ryu, H W

    2001-01-01

    An anaerobic bioleaching of a manganese nodule by anaerobic Mn-reducing bacteria was evaluated for the leaching of metals, Mn, Co, and Ni. Insoluble Mn4+ in the nodule could be reduced to soluble Mn2+ by dissimilatory Mn-reducing bacteria that use a carbon source and Mn4+ as an electron donor and acceptor, respectively. As a result of the Mn reduction, Co and Ni could be leached from the loosed Mn matrix. Leaching experiments were carried out to optimize various process parameters, such as inoculation, pH, temperature, mineral salts, and particle size of the nodule used. The leaching efficiencies of Mn, Co, and Ni increased from 18, 7, and 10% to 77, 70, and 75%, respectively by the inoculation of the Mn-reducing enrichment culture broth. Metals could be efficiently recovered from the nodule in the ranges of pH from 5.0 to 6.5 and temperature from 30 to 45 degrees C by anaerobic bioleaching. External addition of mineral salts was not necessary for Mn, Co, and Ni leaching from the nodule. The optimum ratio of nodule to glucose was 0.1 (w/w). To obtain a leaching efficiency above 70%, the particle size of the nodules must be less than 0.6 mm. PMID:16233110

  20. The Mn-53-Cr-53 System in CAIs: An Update

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.; Wasserburg, G. J.; Bogdanovski, O.

    2005-01-01

    High precision techniques have been developed for the measurement of Cr isotopes on the Triton mass spectrometer, at JPL. It is clear that multiple Faraday cup, simultaneous ion collection may reduce the uncertainty of isotope ratios relative to single Faraday cup ion collection, by the elimination of uncertainties from ion beam instabilities (since ion beam intensities for single cup collection are interpolated in time to calculate isotope ratios), and due to a greatly increased data collection duty cycle, for simultaneous ion collection. Efforts to measure Cr by simultaneous ion collection have not been successful in the past. Determinations on Cr-50-54Cr, by simultaneous ion collection on the Finnigan/ MAT 262 instrument at Caltech, resulted in large variations in extrinsic precision, for normal Cr, of up to 1% in Cr-53/Cr-52 (data corrected for mass fractionation, using Cr-50/Cr-52).

  1. Heat-to-Heat Variation in Creep Life and Fundamental Creep Rupture Strength of 18Cr-8Ni, 18Cr-12Ni-Mo, 18Cr-10Ni-Ti, and 18Cr-12Ni-Nb Stainless Steels

    NASA Astrophysics Data System (ADS)

    Abe, Fujio

    2016-06-01

    Metallurgical factors causing the heat-to-heat variation in time to rupture have been investigated for 300 series stainless steels for boiler and heat exchanger seamless tubes, 18Cr-8Ni (JIS SUS 304HTB), 18Cr-12Ni-Mo (JIS SUS 316HTB), 18Cr-10Ni-Ti (JIS SUS321 HTB), and 18Cr-12Ni-Nb (JIS SUS 347HTB), at 873 K to 1023 K (600 °C to 750 °C) using creep rupture data for nine heats of the respective steels in the NIMS Creep Data Sheets. The maximum time to rupture was 222,705.3 hours. The heat-to-heat variation in time to rupture of the 304HTB and 316HTB becomes more significant with longer test durations at times above ~10,000 hours at 973 K (700 °C) and reaches to about an order of magnitude difference between the strongest and weakest heats at 100,000 hours, whereas that of the 321HTB and 347HTB is very large of about an order of magnitude difference from a short time of ~100 hours to long times exceeding 100,000 hours at 873 K to 973 K (600 °C to 700 °C). The heat-to-heat variation in time to rupture is mainly explained by the effect of impurities: Al and Ti for the 304HTB and 316HTB, which reduces the concentration of dissolved nitrogen available for the creep strength by the formation of AlN and TiN during creep, and boron for the 347HTB, which enhances fine distributions of M23C6 carbides along grain boundaries. The heat-to-heat variation in time to rupture of the 321HTB is caused by the heat-to-heat variation in grain size, which is inversely proportional to the concentration of Ti. The fundamental creep rupture strength not influenced by impurities is estimated for the steels. The 100,000 hours-fundamental creep rupture strength of the 347HTB steel is lower than that of 304HTB and 316HTB at 873 K and 923 K (600 °C and 650 °C) because the slope of stress vs time to rupture curves is steeper in the 347HTB than in the 304HTB and 316HTB. The 100,000 hours-fundamental creep rupture strength of the 321HTB exhibits large variation depending on grain size.

  2. Transient oxidation of multiphase Ni-Cr base alloys

    SciTech Connect

    Baran, G.; Meraner, M.; Farrell, P.

    1988-06-01

    Four commercially available Ni-Cr-based alloys used with porcelain enamels were studied. Major alloying elements were Al, Be, Si, B, Nb, and Mo. All alloys were multiphase. During heat treatments simulating enameling conditions, phase changes occurred in most alloys and were detected using hardness testing, differential thermal analysis (DTA), and microscopy. Oxidation of these alloys at 1000/degrees/C for 10 min produced an oxide layer consisting principally of chromium oxide, but the oxide morphology varied with each alloy depending on the alloy microstructure. Controlling alloy microstructure while keeping the overall composition unchanged may be a means of preventing wrinkled poorly adherent scales from forming.

  3. Heat-to-Heat Variation in Creep Life and Fundamental Creep Rupture Strength of 18Cr-8Ni, 18Cr-12Ni-Mo, 18Cr-10Ni-Ti, and 18Cr-12Ni-Nb Stainless Steels

    NASA Astrophysics Data System (ADS)

    Abe, Fujio

    2016-09-01

    Metallurgical factors causing the heat-to-heat variation in time to rupture have been investigated for 300 series stainless steels for boiler and heat exchanger seamless tubes, 18Cr-8Ni (JIS SUS 304HTB), 18Cr-12Ni-Mo (JIS SUS 316HTB), 18Cr-10Ni-Ti (JIS SUS321 HTB), and 18Cr-12Ni-Nb (JIS SUS 347HTB), at 873 K to 1023 K (600 °C to 750 °C) using creep rupture data for nine heats of the respective steels in the NIMS Creep Data Sheets. The maximum time to rupture was 222,705.3 hours. The heat-to-heat variation in time to rupture of the 304HTB and 316HTB becomes more significant with longer test durations at times above ~10,000 hours at 973 K (700 °C) and reaches to about an order of magnitude difference between the strongest and weakest heats at 100,000 hours, whereas that of the 321HTB and 347HTB is very large of about an order of magnitude difference from a short time of ~100 hours to long times exceeding 100,000 hours at 873 K to 973 K (600 °C to 700 °C). The heat-to-heat variation in time to rupture is mainly explained by the effect of impurities: Al and Ti for the 304HTB and 316HTB, which reduces the concentration of dissolved nitrogen available for the creep strength by the formation of AlN and TiN during creep, and boron for the 347HTB, which enhances fine distributions of M23C6 carbides along grain boundaries. The heat-to-heat variation in time to rupture of the 321HTB is caused by the heat-to-heat variation in grain size, which is inversely proportional to the concentration of Ti. The fundamental creep rupture strength not influenced by impurities is estimated for the steels. The 100,000 hours-fundamental creep rupture strength of the 347HTB steel is lower than that of 304HTB and 316HTB at 873 K and 923 K (600 °C and 650 °C) because the slope of stress vs time to rupture curves is steeper in the 347HTB than in the 304HTB and 316HTB. The 100,000 hours-fundamental creep rupture strength of the 321HTB exhibits large variation depending on grain size.

  4. Ligational behaviour of lomefloxacin drug towards Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO 2(VI) ions: Synthesis, structural characterization and biological activity studies

    NASA Astrophysics Data System (ADS)

    El-Halim, Hanan F. Abd; Mohamed, Gehad G.; El-Dessouky, Maher M. I.; Mahmoud, Walaa H.

    2011-11-01

    Nine new mononuclear Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO 2(VI) complexes of lomefloxacin drug were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, XRD, UV-vis, 1H NMR as well as conductivity and magnetic susceptibility measurements and thermal analyses. The dissociation constants of lomefloxacin and stability constants of its binary complexes have been determined spectrophotometrically in aqueous solution at 25 ± 1 °C and at 0.1 M KNO 3 ionic strength. The discussion of the outcome data of the prepared complexes indicate that the lomefloxacin ligand behaves as a neutral bidentate ligand through OO coordination sites and coordinated to the metal ions via the carbonyl oxygen and protonated carboxylic oxygen with 1:1 (metal:ligand) stoichiometry for all complexes. The molar conductance measurements proved that the complexes are electrolytes. The powder XRD study reflects the crystalline nature for the investigated ligand and its complexes except Mn(II), Zn(II) and UO 2(II). The geometrical structures of these complexes are found to be octahedral. The thermal behaviour of these chelates is studied where the hydrated complexes lose water molecules of hydration in the first steps followed by decomposition of the anions, coordinated water and ligand molecules in the subsequent steps. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. A comparative study of the inhibition zones of the ligand and its metal complexes indicates that metal complexes exhibit higher antibacterial effect against one or more bacterial species than the free LFX ligand. The antifungal and anticancer activities were also tested. The antifungal effect of almost metal complexes is higher than the free ligand. LFX, [Co(LFX)(H 2O) 4]·Cl 2 and [Zn(LFX)(H 2O) 4]·Cl 2 were found to be very active with IC50 values 14, 11.2 and 43.1, respectively. While, other complexes had

  5. Study of the effects of implantation on the high Fe-Ni-Cr and Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Ribarsky, M. W.

    1985-01-01

    A theoretical study of the effects of implantation on the corrosion resistance of Fe-Ni-Cr and Ni-Cr-Al alloys was undertaken. The purpose was to elucidate the process by which corrosion scales form on alloy surfaces. The experiments dealt with Ni implanted with Al, exposed to S at high temperatures, and then analyzed using scanning electron microscopy, scanning Auger spectroscopy and X-ray fluorescence spectroscopy. Pair bonding and tight-binding models were developed to study the compositions of the alloys and as a result, a new surface ordering effect was found which may exist in certain real alloys. With these models, the behavior of alloy constituents in the presence of surface concentrations of O or S was also studied. Improvements of the models to take into account the important effects of long- and short-range ordering were considered. The diffusion kinetics of implant profiles at various temperatures were investigated, and it was found that significant non-equilibrium changes in the profiles can take place which may affect the implants' performance in the presence of surface contaminants.

  6. First-principles investigation of the stability of MN and CrMN precipitates under coherency strains in α-Fe (M = V, Nb, Ta)

    NASA Astrophysics Data System (ADS)

    Fors, Dan H. R.; Wahnström, Göran

    2011-06-01

    We perform a systematic ab initio study of the interface energetics of thin coherent rocksalt (nacl) structured MN and tetragonal CrMN films in bcc Fe (M = V, Nb, Ta), motivated by the vital role of MN and CrMN precipitates for the long-term creep resistance in 9%-12%Cr steels. The similarities and differences in the work of separations and the elastic costs for the coherency strains are identified, and the possibility for formation of coherent films are discussed. Our findings provide valuable information of the interface energetics, which in continuation can be combined with thermodynamical modeling to obtain a better understanding of the initial nucleation stage of the MN and CrMN precipitates, and their influence on the long-term microstructural evolution in 9%-12%Cr steels.

  7. Effect of Cr/C Ratio on Microstructure and Corrosion Performance of Cr3C2-NiCr Composite Fabricated by Laser Processing

    NASA Astrophysics Data System (ADS)

    Lou, Deyuan; Liu, Dun; He, Chunlin; Bennett, Peter; Chen, Lie; Yang, Qibiao; Fearon, Eamonn; Dearden, Geoff

    2016-01-01

    The present study focuses on the effect of different Cr/C ratios on the microstructure, microhardness, and corrosion resistance of Ni-based laser clad hardfacings, reinforced by in situ synthesized chromium carbide particles. Cr3C2-NiCr composites have been laser processed with graphite/Cr/Ni powder blends with varying Cr/C ratios. Following phase analysis (x-ray diffraction) and microstructure investigation (scanning electron microscopy; energy dispersive x-ray analysis; transmission electron microscopy), the solidification of laser melt pool is discussed, and the corrosion resistances are examined. Several different zones (planar, dendritic, eutectic and re-melt zone) were formed in these samples, and the thicknesses and shapes of these zones vary with the change of Cr/C ratio. The sizes and types of carbides and the content of reserved graphite in the composites change as the Cr/C ratio varies. With the content of carbides (especially Cr3C2) grows, the microhardness is improved. The corrosive resistance of the composites to 0.2M H2SO4 aqueous solution decreases as the Cr/C ratio reduces owing to not only the decreasing Cr content in the NiCr matrix but also the galvanic corrosion formed within the carbide and graphite containing Ni matrix.

  8. Spin-driven ordering of Cr in the equiatomic high entropy alloy NiFeCrCo

    NASA Astrophysics Data System (ADS)

    Niu, C.; Zaddach, A. J.; Oni, A. A.; Sang, X.; Hurt, J. W.; LeBeau, J. M.; Koch, C. C.; Irving, D. L.

    2015-04-01

    Spin-driven ordering of Cr in an equiatomic fcc NiFeCrCo high entropy alloy (HEA) was predicted by first-principles calculations. Ordering of Cr is driven by the reduction in energy realized by surrounding anti-ferromagnetic Cr with ferromagnetic Ni, Fe, and Co in an alloyed L12 structure. The fully Cr-ordered alloyed L12 phase was predicted to have a magnetic moment that is 36% of that for the magnetically frustrated random solid solution. Three samples were synthesized by milling or casting/annealing. The cast/annealed sample was found to have a low temperature magnetic moment that is 44% of the moment in the milled sample, which is consistent with theoretical predictions for ordering. Scanning transmission electron microscopy measurements were performed and the presence of ordered nano-domains in cast/annealed samples throughout the equiatomic NiFeCrCo HEA was identified.

  9. Spin-driven ordering of Cr in the equiatomic high entropy alloy NiFeCrCo

    SciTech Connect

    Niu, C.; Zaddach, A. J.; Oni, A. A.; Sang, X.; LeBeau, J. M.; Koch, C. C.; Irving, D. L.; Hurt, J. W.

    2015-04-20

    Spin-driven ordering of Cr in an equiatomic fcc NiFeCrCo high entropy alloy (HEA) was predicted by first-principles calculations. Ordering of Cr is driven by the reduction in energy realized by surrounding anti-ferromagnetic Cr with ferromagnetic Ni, Fe, and Co in an alloyed L1{sub 2} structure. The fully Cr-ordered alloyed L1{sub 2} phase was predicted to have a magnetic moment that is 36% of that for the magnetically frustrated random solid solution. Three samples were synthesized by milling or casting/annealing. The cast/annealed sample was found to have a low temperature magnetic moment that is 44% of the moment in the milled sample, which is consistent with theoretical predictions for ordering. Scanning transmission electron microscopy measurements were performed and the presence of ordered nano-domains in cast/annealed samples throughout the equiatomic NiFeCrCo HEA was identified.

  10. Precipitation sensitivity to alloy composition in Fe-Cr-Mn austenitic steels developed for reduced activation for fusion application

    SciTech Connect

    Maziasz, P.J.; Klueh, R.L.

    1988-01-01

    Special austenitic steels are being designed in which alloying elements like Mo, Nb, and Ni are replaced with Mn, W, V, Ti, and/or Ta to reduce the long-term radioactivity induced by fusion reactor irradiation. However, the new steels still need to have properties otherwise similar to commercial steels like type 316. Precipitation strongly affects strength and radiation-resistance in austenitic steels during irradiation at 400--600/degree/C, and precipitation is also usually quite sensitive to alloy composition. The initial stage of development was to define a base Fe-Cr-Mn-C composition that formed stable austenite after annealing and cold-working, and resisted recovery or excessive formation of coarse carbide and intermetallic phases during elevated temperature annealing. These studies produced a Fe-12Cr-20Mn-0.25C base alloy. The next stage was to add the minor alloying elements W, Ti, V, P, and B for more strength and radiation-resistance. One of the goals was to produce fine MC precipitation behavior similar to the Ti-modified Fe-Cr-Ni prime candidate alloy (PCA). Additions of Ti+V+P+B produced fine MC precipitation along network dislocations and recovery/recrystallization resistance in 20% cold worked material aged at 800/degree/C for 166h, whereas W, Ti, W+Ti, or Ti+P+B additions did not. Addition of W+Ti+V+P+B also produced fine MC, but caused some sigma phase formation and more recrystallization as well. 29 refs., 14 figs., 9 tabs.

  11. Large reversible magnetocaloric effect in Ni-Mn-In-Co

    NASA Astrophysics Data System (ADS)

    Gottschall, Tino; Skokov, Konstantin P.; Frincu, Bianca; Gutfleisch, Oliver

    2015-01-01

    We report on the high irreversible adiabatic temperature change of -8 K in a magnetic field change of 1.95 T in the Heusler compound Ni45.7Mn36.6In13.5Co4.2 showing a first-order magnetostructural transition. Due to the large thermal hysteresis of 10 K, this high ΔTad cannot be obtained in a cyclic way but still the reversible magnetocaloric effect amounts to -3 K—an unexpectedly high value which compares to the ΔTad of La(Fe,Si,Co)13. In order to reveal the nature of this high reversible magnetocaloric effect, in-situ temperature dependent optical microscopy of minor loops of thermal hysteresis has been done.

  12. Nonequilibrium grain-boundary cosegregation of nitrogen and chromium in NiCrMoV steel

    NASA Astrophysics Data System (ADS)

    Zheng, Lei; Xu, Tingdong

    2005-12-01

    It is concluded in this article that nonequilibrium grain-boundary cosegregation (NCGS) of nitrogen and chromium occurs in NiCrMoV steel. That conclusion is reached from experimental observations of the parallel segregation isotherms and the maximum coverage of Cr and N at grain boundaries during the isotherms. This means that the nonequilibrium segregation of Cr induces that of N, in NiCrMoV steel.

  13. Luminescence characteristics of ZnS nanoparticles co-doped with Ni 2+ and Mn 2+

    NASA Astrophysics Data System (ADS)

    Yang, Ping; Lü, Mengkai; Xu, Dong; Yuan, Duorong; Song, Chunfeng; Liu, Suwen; Cheng, Xiufeng

    2003-12-01

    ZnS nanoparticles doped with Ni 2+ and Mn 2+ have been prepared by co-precipitation from homogeneous solutions of Zn, Ni and Mn salt compounds, with S 2- as precipitating anion formed by decomposition of thioacetamide (TAA). X-ray diffraction analysis shows that the average crystalline particle size of the doped and undoped ZnS nanometer scale samples is about 2-4 nm. A novel luminescent property has been observed in the photoluminescence (PL) spectra of the ZnS nanoparticles co-doped with Ni 2+ and Mn 2+. The ZnS nanoparticles can be doped with Ni 2+ and Mn 2+ during synthesis without altering the X-ray diffraction pattern. However, the emission wavelengths (with a color range from blue to green, λem=475-540 nm) and PL intensities of the co-doped samples vary with changing the impurity mole ratios of Ni 2+ and Mn 2+ in the co-doped samples. When the mole ratios of Ni 2+ and Mn 2+ in the co-doped sample are 0.3% and 2.0%, respectively, the relative fluorescence intensity of the co-doped samples is about four times of that of un-doped ZnS nanocrystals. The PL properties of the co-doped samples are dramatically different from those of Ni 2+- and Mn 2+-doped ZnS nanocrystals.

  14. Structural analysis of ferromagnetic Ni-Mn-Sn thin films fabricated by co-sputter deposition

    NASA Astrophysics Data System (ADS)

    Guvenc, Sema; Yumak, Mehmet; Nedelcos, A. Quintana; Llamazares, J. L. Sanchez; Garcia, Carlos Garcia

    2015-03-01

    Ferromagnetic Ni-Mn-X (Sn, In) alloys are predicted as potential candidates for energy efficient Magnetocaloric Effect (MCE) technologies. The MCE is the basis of magnetic refrigeration and it leads to a groundbreaking progress on conventional refrigeration methods. In our research, Ni-Mn-Sn thin films were fabricated by co-sputter deposition method. The Mn losses due to the high Mn vapor pressure produce a deviation from the desired Ni50Mn37Sn13 composition, which are partially compensated by increasing power of the Mn target gun. A systematic study of thin film co-sputter fabrication was divided into three stages; i) a Ni-Mn-Sn target was evaporated at different temperatures in order to study the grain size temperature dependence, ii) the nominal chemical composition (Ni50Mn37Sn13) was reached by controlling the power value applied to the Mn target, iii) the dependence of the phase transformation temperature with the grain size of the thin film alloys was studied. Grain size can be controlled by modifying the substrate temperature (Ts) .

  15. Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3

    NASA Astrophysics Data System (ADS)

    Yahia, H. Ben; Essehli, R.; Avdeev, M.; Park, J.-B.; Sun, Y.-K.; Al-Maadeed, M. A.; Belharouak, I.

    2016-06-01

    The new compounds NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 were synthesized by sol-gel method and their crystal structures were determined by using neutron powder diffraction data. These compounds were characterized by galvanometric cycling and cyclic voltammetry. NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 crystallize with a stuffed α-CrPO4-type structure. The structure consists of a 3D-framework made of octahedra and tetrahedra that are sharing corners and/or edges generating channels along [100] and [010], in which the sodium atoms are located. Of significance, in the structures of NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 a statistical disorder Ni2+/Cr3+ was observed on both the 8g and 4a atomic positions, whereas in NaCoCr2(PO4)3 the statistical disorder Co2+/Cr3+ was only observed on the 8g atomic position. When tested as negative electrode materials, NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 delivered specific capacities of 352, 385, and 368 mA h g-1, respectively, which attests to the electrochemical activity of sodium in these compounds.

  16. Environmentally Assisted Cracking of Commercial Ni-Cr-Mo Alloys - A Review

    SciTech Connect

    Rebak, R B

    2004-11-09

    Nickel-Chromium-Molybdenum alloys (Ni-Cr-Mo) are highly resistant to general corrosion, localized corrosion and environmentally assisted cracking (EAC). Cr acts as a beneficial element under oxidizing acidic conditions and Mo under reducing conditions. All three elements (Ni, Cr and Mo) act synergistically to provide resistance to EAC in environments such as hot concentrated chloride solutions. Ni-Cr-Mo alloys may suffer EAC in environments such as hot caustic solutions, hot wet hydrofluoric acid (HF) solutions and in super critical water oxidation (SCWO) applications. Not all the Ni-Cr-Mo alloys have the same susceptibility to cracking in the mentioned environments. Most of the available data regarding EAC is for the oldest Ni-Cr-Mo alloys such as N10276 and N06625.

  17. Structural and magnetic properties of Ni/Mn codoped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Vijayaprasath, G.; Murugan, R.; Asaithambi, S.; Sakthivel, P.; Mahalingam, T.; Ravi, G.

    2016-05-01

    We report systematic studies of the magnetic properties of Ni and Mn co-doped ZnO nanoparticles prepared by co-precipitation method. Structural characterization reveals that Ni and Mn ions substituted into ZnO lattices without any secondary phases formation. Photoluminescence and Raman spectra shows that the Ni/Mn were doped into the ZnO lattice resulting slight shift in near-band-edge emission. Moreover, the novel Raman peak at 586 cm-1 indicates two kinds of cations via doping that could affect the local polarizability. Magnetic measurements of the nanoparticles exhibits ferromagnetic behavior at room-temperature.

  18. From ferromagnetic{endash}ferromagnetic to ferromagnetic{endash}antiferromagnetic exchange coupling in NiFe/MnNi bilayers

    SciTech Connect

    Spenato, David; Youssef, Jamal Ben; Le Gall, Henri; Ostorero, Jean

    2001-06-01

    The effect of the growth conditions and the Mn concentration on the exchange coupling between a ferromagnetic (F) NiFe and an antiferromagnetic (AF) MnNi layers were studied. We found that an F/AF coupling appears in the bilayers when the Mn concentration is more than 45%. Beyond this critical concentration the exchange field shows a maximum then decreases. The correlation between the exchange field and the microstructure of the film is discussed. We show that: (1) the enhancement of the exchange field is associated with the enhancement of the antiferromagnetic grain size and (2) the existence of the exchange field is associated with a third x-ray peak which may be an FeMnNi ternary allow type. This result was associated with interfacial diffusion confirmed by magnetization variation measurements before and after annealing. {copyright} 2001 American Institute of Physics.

  19. Entropic and magnetic properties of Ni-Mn-In magnetocaloric materials

    NASA Astrophysics Data System (ADS)

    Chen, Jing-Han; Bruno, Nickolaus; Karaman, Ibrahim; Huang, Yujin; Li, Jianguo; Ross, Joseph H., Jr.

    2015-03-01

    We report magnetization and field-dependent calorimetry studies of phase transitions in Ni-Mn-In. Off-stoichiometric alloys based on NiMnIn have drawn attention due to the coupled first order magnetic and structural transformation, and the large magnetocaloric entropy associated with this martensitic transformation. We have analyzed materials with compositions NiMnIn, NiMnInand NiMnIn, which differ in that the former exhibits a paramagnetic to antiferromagnetic transition, while the others exhibit an additional ferromagnetic transition. Our results show that in the Nimaterials, the total entropy change at the phase transition can be modeled solely according to a magnetic contribution due to local moments on the Mn sites. On the other hand, NiMnInincludes a larger contribution which can be described in terms of a magneto-elastic coupling. This we will discuss in terms of the Bean-Rodbell model and a renomalization of the Debye temperature coupled with magnetism. We will also discuss the low-temperature properties, which show divergent behavior including antiferromagnetic, ferrimagnetic and superparamagnetic behavior. We gratefully acknowledge the support from NSF-DMR and the Robert A. Welch Foundation.

  20. [XPS and UPS characterization for Cr and Mn in high-temperature oxide films of bulk nanocrystalline 304 stainless steel].

    PubMed

    Xu, Song-Ning; Wang, Sheng-Gang; Han, Hai-Bao; Sun, Nai-Kun

    2013-03-01

    The authors studied the binding energies of valence electrons of two oxide scales, the atomic percentages of Cr and Mn elements in two oxide films, the work function of two oxide films on bulk nanocrystalline 304 stainless steel (BN-SS304) and conventional polycrystalline 304 stainless steel (CP-SS304). BN-SS304 was prepared by severe rolling technique, and the two oxide films were formed in atmosphere at 900 degrees C for 24 hours oxidation on BN-SS304 and CP-SS304 surfaces. In the two oxide films, Cr and Mn elements exist in the forms of Cr3+, Cr0, Mn4+ and Mn0. The atomic percentage ratios of Cr+ / (Cr3+ + Cr0) and Mn4+ / (Mn4+ + Mn0) in the oxide film on BN-SS304 are lower than those in the oxide film on CP-SS304. The interactions of the two oxides and the valence electrons of elements are Mn-O, Cr-O,3d and 4s of Mn0 and Cr0. The binding energies of the valence electrons in the oxide film on BN-SS304 are larger than those in the oxide film on CP-SS304, the work function of the oxide film on BN-SS304 is 0.07 eV larger than that on CP-SS304. PMID:23705465

  1. Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

    SciTech Connect

    Ohno, S.; Shimakura, H.; Tahara, S.; Okada, T.

    2015-08-17

    The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.

  2. Excess Ni-doping induced enhanced room temperature magneto-functionality in Ni-Mn-Sn based shape memory alloy

    SciTech Connect

    Pramanick, S.; Giri, S.; Majumdar, S.; Chatterjee, S.

    2014-09-15

    Present work reports on the observation of large magnetoresistance (∼−30% at 80 kOe) and magnetocaloric effect (∼12 J·kg{sup −1}·K{sup −1} for 0–50 kOe) near room temperature (∼290 K) on the Ni-excess ferromagnetic shape memory alloy Ni{sub 2.04}Mn{sub 1.4}Sn{sub 0.56}. The sample can be thought of being derived from the parent Ni{sub 2}Mn{sub 1.4}Sn{sub 0.6} alloy, where excess Ni was doped at the expense of Sn. Such Ni doping enhances the martensitic transition temperature and for the Ni{sub 2.04}Mn{sub 1.4}Sn{sub 0.56} it is found to be optimum (288 K). The doped alloy shows enhanced magneto-functional properties as well as reduced saturation magnetization as compared to the undoped counterpart at low temperature. A probable increment of antiferromagnetic correlation between Mn-atoms on Ni substitution can be accounted for the enhanced magneto-functional properties as well as reduction in saturation moment.

  3. Excess Ni-doping induced enhanced room temperature magneto-functionality in Ni-Mn-Sn based shape memory alloy

    NASA Astrophysics Data System (ADS)

    Pramanick, S.; Chatterjee, S.; Giri, S.; Majumdar, S.

    2014-09-01

    Present work reports on the observation of large magnetoresistance (˜-30% at 80 kOe) and magnetocaloric effect (˜12 J.kg-1.K-1 for 0-50 kOe) near room temperature (˜290 K) on the Ni-excess ferromagnetic shape memory alloy Ni2.04Mn1.4Sn0.56. The sample can be thought of being derived from the parent Ni2Mn1.4Sn0.6 alloy, where excess Ni was doped at the expense of Sn. Such Ni doping enhances the martensitic transition temperature and for the Ni2.04Mn1.4Sn0.56 it is found to be optimum (288 K). The doped alloy shows enhanced magneto-functional properties as well as reduced saturation magnetization as compared to the undoped counterpart at low temperature. A probable increment of antiferromagnetic correlation between Mn-atoms on Ni substitution can be accounted for the enhanced magneto-functional properties as well as reduction in saturation moment.

  4. Nanoscale Cellular Structures at Phase Boundaries of Ni-Cr-Al-Ti and Ni-Cr-Mo-Al-Ti Superalloys

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Dunand, David C.

    2015-06-01

    The microstructural evolution of Ni-20 pct Cr wires was studied during pack cementation where Al and Ti, with and without prior cementation with Mo, are deposited to the surface of the Ni-Cr wires and subsequently homogenized in their volumes. Mo deposition promotes the formation of Kirkendall pores and subsequent co-deposition of Al and Ti creates a triple-layered diffusional coating on the wire surface. Subsequent homogenization drives the alloying element to distribute evenly in the wires which upon further heat treatment exhibit the γ + γ' superalloy structure. Unexpectedly, formation of cellular structures is observed at some of the boundaries between primary γ' grains and γ matrix grains. Based on additional features ( i.e., ordered but not perfectly periodic structure, confinement at γ + γ' phase boundaries as a cellular film with ~100 nm width, as well as lack of topologically close-packed phases), and considering that similar, but much larger, microstructures were reported in commercial superalloys, it is concluded that the present cellular structure solidified as a thin film, composed of eutectic γ + γ' and from which the γ' phase was subsequently etched, which was created by incipient melting of a region near the phase boundary with high solute segregation.

  5. NiAl-based Polyphase in situ Composites in the NiAl-Ta-X (X = Cr, Mo, or V) Systems

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Polyphase in situ composites were generated by directional solidification of ternary eutectics. This work was performed to discover if a balance of properties could be produced by combining the NiAl-Laves phase and the NiAl-refractory metal phase eutectics. The systems investigated were the Ni-Al-Ta-X (X = Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and the eutectic composition, temperature, and morphology were determined. The ternary eutectic systems examined were the NiAl-NiAlTa-(Mo, Ta), NiAl-(Cr, Al) NiTa-Cr, and the NiAl-NiAlTa-V systems. Each eutectic consists of NiAl, a C14 Laves phase, and a refractory metal phase. Directional solidification was performed by containerless processing techniques in a levitation zone refiner to minimize alloy contamination. Room temperature fracture toughness of these materials was determined by a four-point bend test. Preliminary creep behavior was determined by compression tests at elevated temperatures, 1100-l400 K. Of the ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr, Al)NiTa-Cr eutectic was intermediate between the values of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  6. Study of the preparation of NI-Mn-Zn ferrite using spent NI-MH and alkaline Zn-Mn batteries

    NASA Astrophysics Data System (ADS)

    Xi, Guoxi; Xi, Yuebin; Xu, Huidao; Wang, Lu

    2016-01-01

    Magnetic nanoparticles of Ni-Mn-Zn ferrite have been prepared by a sol-gel method making use of spent Ni-MH and Zn-Mn batteries as source materials. Characterization by X-ray diffraction was carried out to study the particle size. The presence of functional groups was identified by Fourier transform infrared spectroscopy. From studies by thermogravimetry and differential scanning calorimetry, crystallization occurred at temperatures above 560 °C. The magnetic properties of the final products were found to be directly influenced by the average particle size of the product. The Ms values increase and the Hc values decrease as the size of the Ni-Mn-Zn ferrite particles increases.

  7. Influence of Bulk Chemical Composition on Relative Sensitivity Factors for 55Mn/52Cr by SIMS: Implications for the 53Mn-53Cr Chronometer

    SciTech Connect

    Matzel, J; Jacobsen, B; Hutcheon, I D; Kita, N; Ryerson, F J

    2009-09-09

    The {sup 53}Mn-{sup 53}Cr systematics of meteorite samples provide an important high resolution chronometer for early solar system events. Accurate determination of the initial abundance of {sup 53}Mn ({tau}{sub 1/2} = 3.7 Ma) by secondary ion mass spectrometry (SIMS) is dependent on properly correcting for differing ion yields between Mn and Cr by use of a relative sensitivity factor (RSF). Ideal standards for SIMS analysis should be compositionally and structurally similar to the sample of interest. However, previously published Mn-Cr studies rely on few standards (e.g., San Carlos olivine, NIST 610 glass) despite significant variations in chemical composition. We investigate a potential correlation between RSF and bulk chemical composition by determining RSFs for {sup 55}Mn/{sup 52}Cr in 11 silicate glass and mineral standards (San Carlos olivine, Mainz glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, BM90/21-G, and T1-G, NIST 610 glass, and three LLNL pyroxene-composition glasses). All standards were measured on the Cameca ims-3f ion microprobe at LLNL, and a subset were also measured on the Cameca ims-1270 ion microprobe at the Geological Survey of Japan. The standards cover a range of bulk chemical compositions with SiO{sub 2} contents of 40-71 wt.%, FeO contents of 0.05-20 wt.% and Mn/Cr ratios between 0.4 and 58. We obtained RSF values ranging from 0.83 to 1.15. The data obtained on the ims-1270 ion microprobe are within {approx}10% of the RSF values obtained on the ims-3f ion microprobe, and the RSF determined for San Carlos olivine (0.86) is in good agreement with previously published data. The typical approach to calculating an RSF from multiple standard measurements involves making a linear fit to measured {sup 55}Mn/{sup 52}Cr versus true {sup 55}Mn/{sup 52}Cr. This approach may be satisfactory for materials of similar composition, but fails when compositions vary significantly. This is best illustrated by the {approx}30% change in RSF we see between

  8. Enhanced magnetic refrigeration properties in Mn-rich Ni-Mn-Sn ribbons by optimal annealing

    PubMed Central

    Zhang, Yu; Zhang, Linlin; Zheng, Qiang; Zheng, Xinqi; Li, Ming; Du, Juan; Yan, Aru

    2015-01-01

    The influence of annealing time on temperature range of martensitic phase transition (ΔTA-M), thermal hysteresis (ΔThys), magnetic hysteresis loss (ΔMhys), magnetic entropy change (ΔSM) and relative refrigeration capacity (RC) of the Mn-rich Ni43Mn46Sn11 melt spun ribbons have been systematically studied. By optimal annealing, an extremely large ΔSM of 43.2 J.kg−1K−1 and a maximum RC of 221.0 J.kg−1 could be obtained respectively in a field change of 5 T. Both ΔTA-M and ΔThys decreases after annealing, while ΔMhys and ΔSM first dramatically increase to a maximum then degenerates as increase of annealing time. A large effective cooling capacity (RCeff) of 115.4 J.kg−1 was achieved in 60 min annealed ribbons, which increased 75% compared with that unannealed ribbons. The evolution of magnetic properties and magnetocaloric effect has been discussed and proved by atomic ordering degree, microstructure and composition analysis. PMID:26055884

  9. Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

    SciTech Connect

    Nicholson, Don M; Odbadrakh, Khorgolkhuu; Rios, Orlando; Hodges, Jason P; Ludtka, Gerard Michael; Porter, Wallace D; Sefat, A. S.; Rusanu, Aurelian; Evans III, Boyd Mccutchen

    2012-01-01

    Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system have been explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering (LSMS) method to explore the magnetic states responsible for the magnet-caloric effect in this material. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy were investigated using differential scanning calorimetry (DSC) and superconducting quantum interference device (SQUID). Neutron scattering experiments were performed to observe the structural and magnetic phase transformations at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on alloys of Ni-Mn-Ga and Ni-Mn-Ga-Cu-Fe. Data from the observations are discussed in comparison with the computational studies.

  10. Exchange bias effects in Heusler alloy Ni2MnAl/Fe bilayers

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Tomoki; Kubota, Takahide; Sugiyama, Tomoko; Huminiuc, Teodor; Hirohata, Atsufumi; Takanashi, Koki

    2016-06-01

    Ni2MnAl Heusler alloy thin films were epitaxially grown on MgO(1 0 0) single crystal substrates by ultra-high-vacuum magnetron sputtering technique. X-ray diffraction and transmission electron microscopy observation revealed that the structures of all the Ni2MnAl thin films were B2-ordered regardless of the deposition temperature ranging from room temperature to 600 °C. The temperature dependence of electrical resistivity showed a kink about 280 K, which was consistent with a reported value of the Néel temperature for antiferromagnetic B2-Ni2MnAl. The magnetization curves of Ni2MnAl/Fe bilayer samples showed a shift caused by the interfacial exchange interaction at 10 K. The maximum value of the exchange bias field H ex was 55 Oe corresponding to the exchange coupling energy J k of 0.03 erg cm‑2.

  11. Possible martensitic transformation and ferrimagnetic properties in Heusler alloy Mn2NiSn

    NASA Astrophysics Data System (ADS)

    Duan, Ying-Ni; Fan, Xiao-Xi; Kutluk, Abdugheni; Du, Xiu-Juan; Zhang, Zheng-Wei; Song, Yu-Ling

    2015-07-01

    The electronic structure and magnetic properties of Hg2CuTi-type Mn2NiSn have been studied by performing the first-principle calculations. It is found that the phase transformation from the cubic to the tetragonal structure reduces the total energy, indicating that the martensitic phase is more stable and the phase transition from austenite to martensite may happen at low temperature for Hg2CuTi-type Mn2NiSn. Concerning the magnetism of Hg2CuTi-type Mn2NiSn, both austenitic and martensitic phases are suggested to be ferrimagnets. Furthermore, martensitic transformation decreases the magnetic moment per formula unit compared with austenitic phase. The results are helpful to accelerate the use of Mn2NiSn alloys in the series for magnetic shape memory applications.

  12. Low temperature magneto-structural transitions in Mn3Ni20P6

    NASA Astrophysics Data System (ADS)

    Cedervall, Johan; Beran, Premysl; Vennström, Marie; Danielsson, Therese; Ronneteg, Sabina; Höglin, Viktor; Lindell, David; Eriksson, Olle; André, Gilles; Andersson, Yvonne; Nordblad, Per; Sahlberg, Martin

    2016-05-01

    X-ray and neutron powder diffraction has been used to determine the crystal and magnetic structure of Mn3Ni20P6. The crystal structure can be described as cubic with space group Fm 3 barm (225) without any nuclear phase transformation within studied temperature interval from room temperature down to 4 K. The magnetic structure of Mn3Ni20P6 is complex with two independent magnetic positions for the Mn atoms and the compound passes three successive magnetic phase transitions during cooling. At 30 K the spins of the Mn atoms on the Wyckoff 4a site (Mn1) order to form a primitive cubic antiferromagnetic structure with propagation vector k=(0 0 1). Between 29 and 26 K the Mn atoms on the Wyckoff 8c site (Mn2) order independently on already ordered Mn1 magnetic structure forming a commensurate antiferromagnetic structure with propagation vector k=(0 0 ½) and below 26 K, both Mn positions order to form an incommensurate helical structure with propagation vector k=(0 0 ~0.45). Magnetization vs. temperature curve of Mn3Ni20P6 shows a steep increase indicating some magnetic ordering below 230 K and a sharp field dependent anomaly in a narrow temperature range around 30 K.

  13. Microstructural studies of nanocomposite thin films of Ni/CrN prepared by reactive magnetron sputtering.

    PubMed

    Kuppusami, P; Thirumurugesan, R; Divakar, R; Kataria, S; Ramaseshan, R; Mohandas, E

    2009-09-01

    Synthesis and characterization of nanocomposites of Ni/CrN thin films prepared by DC magnetron sputtering from a target of 50 wt.%Ni-50 wt.%Cr is investigated. The films prepared as a function of nitrogen flow rate and substrate temperature showed that the films contained Ni and CrN phases with crystallite sizes in the nanometer range. Measurement of nanomechanical properties of the composite films exhibited a significant decrease in the values of hardness and Young's modulus than those of pure CrN films. PMID:19928270

  14. Diffusional creep and creep-degradation in dispersion-strengthened Ni-Cr base alloys.

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1973-01-01

    Dispersoid-free regions were observed in the dispersion-strengthened alloy TD-NiCr (Ni-20 Cr-2 ThO2) after slow strain rate testing (stress rupture, creep, and fatigue) in air from 1145 to 1590 K. Formation of the dispersoid-free regions appears to be the result of diffusional creep. The net effect of creep in TD-NiCr is the degradation of the alloy to a duplex microstructure. Creep degradation of TD-NiCr is further enhanced by the formation of voids and intergranular oxidation in the dispersoid-free bands. Void formation was observed after as little as 0.13% creep deformation at 1255 K. The dispersoid-free regions apparently provide sites for void formation and oxide growth since the strength and oxidation resistance of Ni-20 Cr-2 ThO2.

  15. Oxidation behavior of TD-NiCr in a dynamic high temperature environment

    NASA Technical Reports Server (NTRS)

    Tenney, D. R.; Young, C. T.; Herring, H. W.

    1974-01-01

    The oxidation behavior of TD-NiCr has been studied in static and high-speed flowing air environments at 1100 and 1200 C. It has been found that the stable oxide morphologies formed on the specimens exposed to the static and dynamic environments were markedly different. The faceted crystal morphology characteristic of static oxidation was found to be unstable under high-temperature, high-speed flow conditions and was quickly replaced by a porous NiO 'mushroom' type structure. Also, it was found that the rate of formation of CrO3 from Cr2O3 was greatly enhanced by high gas velocity conditions. The stability of Cr2-O3 was found to be greatly improved by the presence of an outer NiO layer, even though the NiO layer was very porous. An oxidation model is proposed to explain the observed microstructures and overall oxidation behavior of TD-NiCr alloys.

  16. Magnetic structures of nanometer scale Dy, Cr and Ni

    SciTech Connect

    Fitzsimmons, M.R.; Robinson, R.A.; Lawson, A.C.; Kwei, G.H.; Sickafus, K.E.; Eastman, J.A.; Burkel, E.

    1992-10-01

    Materials composed of nanometer-sized structures are becoming technologically relevant as the sizes of electronic devices approach the nanometer scale. Questions as to the performance and durability of these devices can be partially addressed through the characterization and understanding of the magnetic structures and properties of nanometer-sized materials. The purpose of the present work is to understand the relationship between the microstructure of nanocrystalline materials and their magnetic structures and properties. This paper summarizes three separate experiments: (1) an X-ray diffraction and anomalous absorption (XANES) study of nanocrystalline Dy, (2) neutron diffraction measurements of the magnetic structure of nanocrystalline Cr, and (3) the measurement of the magnetization density of a single twist grain boundary in Ni.

  17. Synthesis of nanostructured Cr{sub 3}C{sub 2}-25(Ni20Cr) coatings

    SciTech Connect

    He, J.; Ice, M.; Lavernia, E.J.

    2000-02-01

    On the basis of the nanocrystalline Cr{sub 3}C{sub 2}-25 (Ni20 Cr) feedstock powders produced by mechanical milling, a nanostructured coating has been synthesized using high velocity oxygen fuel (HVOF) thermal spraying. The properties of the nanostructured coating were compared to those of the conventional coating of the same composition using scanning electron microscope (SEM), transmission electron microscope (TEM), and microhardness tests. The nanostructured Cr{sub 3}C{sub 2}-25 (Ni20Cr) coating synthesized in this study had an average carbide particle size of 24 nm. Discontinuous elongated amorphous phases were observed in the nanostructured coating. The conventional Cr{sub 3}C{sub 2}-25 (Ni20Cr) coatings produced using blended elemental powders exhibited an inhomogeneous microstructure. The observed homogeneity of the nanostructured coating is attributed, in part, to the microstructural improvement of the starting powder. The nanostructured Cr{sub 3}C{sub 2}-25 (Ni20Cr) coating yielded an average microhardness value of 1020 DPH{sub 300}, which corresponds to a 20 pct increase in microhardness over that of the conventional coating. The nanostructured cr{sub 3}C{sub 2}-25 (Ni20Cr) coating also exhibited a higher apparent fracture toughness relative to that of the conventional coating. The apparent mechanical property improvements in the nanostructured coating were though to result from the uniformity of the microstructure and the high performance associated with a nanostructured structure. In addition, the mechanism that is present during the milling of a system containing nondeformable particles is discussed in light of the TEM observations.

  18. Microstructure of laser clad Ni- Cr- Al- Hf alloy on a γ' strengthened ni- base superalloy

    NASA Astrophysics Data System (ADS)

    Singh, Jogender; Mazumder, J.

    1988-08-01

    Alloys and coatings for alloys for improved high temperature service life under aggressive atmo-spheres are of great contemporary interest. There is a general consensus that the addition of rare earths such as Hf will provide many beneficial effects for such alloys. The laser cladding technique was used to produce Ni-Cr-AI-Hf alloys with extended solid solution of Hf. A 10 kW CO2 laser with mixed powder feed was used for laser cladding. Optical, scanning electron (SEM) and scanning transmission electron (STEM) microscopy were employed to characterize the microstructure of alloys produced during laser cladding processes. Microstructural studies revealed grain refinement, considerable in-crease in solubility of Hf in the matrix, Hf-rich precipitates, and new metastable phases. The size and morphology of γ' (Ni3Al) phase were discussed in relation to its microchemistry and the laser processing conditions. This paper will report the microstructural development in this laser clad Ni-Cr-AI-Hf alloy.

  19. Prolidase-Associated Trace Elements (Mn, Zn, Co, and Ni) in the Patients with Parkinson's Disease.

    PubMed

    Verma, Akhilesh Kumar; Keshari, Anand Kumar; Raj, Janak; Kumari, Renu; Kumar, Tarun; Sharma, Vivek; Singh, Tej Bali; Srivastava, Shalabh; Srivastava, Ragini

    2016-05-01

    Micronutrients and trace elements have been identified to play an important role in the development of Parkinson's disease (PD). In our previous study, we observed that prolidase activity is associated with oxidative stress and progression of PD. In present study, we aimed to study the association of prolidase-associated trace elements, such as Co, Mn, Ni, and Zn in the plasma of patients with PD by inductively coupled plasma spectrometry. Plasma levels of Co, Mn, and Ni were significantly increased, whereas plasma levels of Zn was significantly decreased (all P < 0.05) in the patients with PD than healthy controls. Plasma prolidase activity was not correlated to its associated trace elements in PD. A positive, linear, and significant correlation was observed between age and Co, and Mn, and Ni while negative and non-significant between age and status of Zn in the patients. Co, Mn, and Ni were continually elevated with increase in age as well as duration of disease in the patients with PD, whereas status of Zn was continually decreased. Thus, the study concluded that trace elements Co, Ni, and Mn status were increased and Zn status was decreased in the plasma of patients with PD. It is also concluded that elevated Co, Mn, and Ni has been associated with progression of Parkinson's disease. PMID:26364956

  20. Mesoporous hybrid NiOx-MnOx nanoprisms for flexible solid-state asymmetric supercapacitors.

    PubMed

    Wei, Chengzhen; Cheng, Cheng; Ma, Lan; Liu, Mengna; Kong, Dechen; Du, Weimin; Pang, Huan

    2016-06-28

    Mesoporous hybrid NiOx-MnOx nanoprisms have been successfully prepared in this work. The synthesis process involves a facile solvothermal method for preparation of Ni-Mn precursor particles and a subsequent annealing treatment. These mesoporous hybrid NiOx-MnOx nanoprisms have a high surface area of 101.6 m(2) g(-1). When evaluated as electrode materials in supercapacitors, the as-prepared mesoporous hybrid NiOx-MnOx nanoprisms deliver a specific capacitance of 1218 F g(-1) at a current density of 2.0 A g(-1). More importantly, the mesoporous hybrid NiOx-MnOx nanoprisms were successfully used to construct flexible solid-state asymmetric supercapacitors. The device shows a specific capacitance of 149.1 mF cm(-2) at 2.0 mA cm(-2), a good cycling stability with only 2.9% loss of capacitance after 5000 charge-discharge cycles, and good mechanical flexibility under different bending angles. These results support the promising application of mesoporous hybrid NiOx-MnOx nanoprisms as advanced supercapacitor materials. PMID:27295406

  1. Local valence and magnetic characteristics of La2NiMnO6

    SciTech Connect

    Guo, HZ; Gupta, A.; Varela del Arco, Maria; Pennycook, Stephen J; Zhang, J

    2009-01-01

    Epitaxial thin films of ordered double perovskite La{sub 2}NiMnO{sub 6} have been studied by a combination of high-resolution scanning transmission electron microscopy, quantitative electron energy loss spectroscopy, x-ray absorption spectroscopy, and x-ray magnetic circular dichroism (XMCD) spectroscopy. Our results show the nominal oxidation states of Ni and Mn ions to be Ni{sup 2+} and Mn{sup 4+} thus the ferromagnetism in ground state is mainly due to Ni{sup 2+}-O-Mn{sup 4+} superexchange interactions. In addition, short-range ferromagnetic correlations are observed above the Curie temperature (T{sub c} {approx} 280 K) from XMCD measurement, which are likely induced by antisite defects against long-range ordering of the Ni/Mn sublattice. The XMCD results also demonstrate that the Ni{sup 2+} and Mn{sup 4+} ions are ferromagnetically aligned but exhibit large differences in the spin and orbital contributions to their effective magnetic moments.

  2. Unique Sandwiched Carbon Sheets@Ni-Mn Nanoparticles for Enhanced Oxygen Evolution Reaction.

    PubMed

    Zhang, Yan; Zhang, Huijuan; Yang, Jiao; Bai, Yuanjuan; Qiu, Huajun; Wang, Yu

    2016-05-11

    A unique sandwich-like architecture, where Ni-Mn nanoparticles are enveloped in coupled carbon sheets (CS@Ni-Mn), has been successfully fabricated. In the synthesis process, a great quantity of uniform NiMnO3 nanosheets generated by a universal hydrothermal method acts as precursors and templates and the cheap, environmentally friendly and recyclable glucose functions as a green carbon source. Via subsequent hydrothermal reaction and thermal annealing, sandwiched nanocomposites with Ni-Mn nanoparticles embedded inside and carbon sheets encapsulating outside can be massively prepared. The novel sandwich-like CS@Ni-Mn possesses numerous advantages, such as an intrinsic porous feature, large specific surface area, and enhanced electronic conductivity. Moreover, as a promising NiMn-based oxygen evolution reaction (OER) catalyst, the special sandwiched nanostructure demonstrates improved electrochemical properties in 1 M KOH, including a low overpotential of about 250 mV, a modest Tafel slope of 40 mV dec(-1), excellent stability over 2000 cycles, and durability for 40 h. PMID:27101350

  3. Ternary NiFeMn layered double hydroxides as highly-efficient oxygen evolution catalysts.

    PubMed

    Lu, Zhiyi; Qian, Li; Tian, Yang; Li, Yaping; Sun, Xiaoming; Duan, Xue

    2016-01-18

    Layered double hydroxides (LDHs) are a family of layer materials that receive heightened attention. Herein a ternary NiFeMn-LDH is investigated with superior oxygen evolution activity, which is attributed to the Mn(4+) doping in the intralayer, which modifies the electronic structure and improves the conductivity of the electrocatalyst. PMID:26579843

  4. Hot Corrosion Behavior of Bare, Cr3C2-(NiCr) and Cr3C2-(NiCr) + 0.2wt.%Zr Coated SuperNi 718 at 900 °C

    NASA Astrophysics Data System (ADS)

    Mudgal, Deepa; Singh, Surendra; Prakash, Satya

    2015-01-01

    Corrosion in incinerators, power plants, and chemical industries are frequently encountered due to the presence of salts containing sodium, sulphur, and chlorine. To obviate this problem, bare and coated alloys were tested under environments simulating the conditions present inside incinerators and power plants. 0.2 wt.% zirconium powder was incorporated in the Cr3C2-(NiCr) coating powder. The original powder and Zr containing powder was sprayed on Superni 718 alloy by D-gun technique. The bare and coated alloys were tested under Na2SO4 + K2SO4 + NaCl + KCl and Na2SO4 + NaCl environment. The corrosion rate of specimens was monitored using weight change measurements. Characterization of the corrosion products has been done using FE-SEM/EDS and XRD techniques. Bare and coated alloys showed very good corrosion resistance under given molten salt environments. Addition of 0.2wt.%Zr in Cr3C2-25%(NiCr) coating further greatly reduced the oxidation rate as well as improved the adherence of oxide scale to the coating surface during the time of corrosion.

  5. Cr, Cu, Mn, Mo, Ni, and Steel Price Drivers

    USGS Publications Warehouse

    Papp, John F.; Corathers, Lisa A.; Edelstein, Daniel L.; Fenton, Michael D.; Kuck, Peter H.; Magyar, Michael J.

    2007-01-01

    Summary This report contains the 55 slide images from a presentation made by the author at the meeting of the Metal Powder Industries Federation held in Denver, CO, on May 15, 2007. The Metal Powder Industries Federation (MPIF) invited the U.S. Geological Survey (USGS) to speak at their annual meeting about the price drivers for chromium, copper, manganese, molybdenum, nickel, and steel. These metals are of interest to MPIF because the prices of these raw materials used by their industry were at historically high levels. Because the USGS closely monitors, yet neither buys nor sells, metal commodities, it is an unbiased source of metal price information and analysis. The authors used information about these and other metals collected and published by the USGS (U.S. production, trade, stocks, and prices) and about consumption and stocks internationally by country from industry organizations that publish such information, because metal markets are influenced by activities and events over the entire globe. By seeking a common cause for common behavior among the various metal commodities, the authors found that major price drivers on metal commodities were inflation, major international events such as wars and recessions, and major national events such as the dissolution of the Soviet Union in 1991 and economic growth in China, which started with the open door policy in the 1970s but did not have significant market impact until starting in the 1990s. Metal commodity prices also responded to commodity-specific events.

  6. Multiferroicity in B-site ordered double perovskite Y2MnCrO6

    NASA Astrophysics Data System (ADS)

    Fang, Yong; Yan, Shi-Ming; Qiao, Wen; Wang, Wei; Wang, Dun-Hui; Du, You-Wei

    2014-11-01

    Double perovskite manganite Y2MnCrO6 ceramic is synthesized and its multiferroic properties are investigated. Novel multiferroic properties are displayed with respect to other multiferroics, such as high ferroelectric phase transition temperature, and the coexistence of ferrimagnetism and ferroelectricity. Moreover, the ferroelectric polarization of Y2MnCrO6 below the magnetic phase temperature can be effectively tuned by an external magnetic field, showing a remarkable magnetoelectric effect. These results open an effective avenue to explore magnetic multiferroics with spontaneous magnetization and ferroelectricity, as well as a high ferroelectric transition temperature.

  7. Oxidation behavior of cubic phases formed by alloying Al3Ti with Cr and Mn

    NASA Technical Reports Server (NTRS)

    Parfitt, L. J.; Nic, J. P.; Mikkola, D. E.; Smialek, J. L.

    1991-01-01

    Gravimetric, SEM, and XRD data are presented which document the significant improvement obtainable in the oxidation resistance of Al3Ti-containing alloys through additions of Cr. The L1(2) Al(67)Cr(8)Ti25 alloy exhibited excellent cyclic oxidation resistance at 1473 K, with the primary oxide formed being the ideally protective alpha-Al2O3. The Al(67)Mn(8)Ti(25) alloy also tested for comparison exhibited poor cyclic oxidation resistance, with substantial occurrence of TiO2 in the protective scales. Catastrophic oxidation was also encountered in the quaternary alloy Al(67)Mn(8)Ti(22)V(3).

  8. Exchange bias of Ni nanoparticles embedded in an antiferromagnetic IrMn matrix

    NASA Astrophysics Data System (ADS)

    Kuerbanjiang, Balati; Wiedwald, Ulf; Haering, Felix; Biskupek, Johannes; Kaiser, Ute; Ziemann, Paul; Herr, Ulrich

    2013-11-01

    The magnetic properties of Ni nanoparticles (Ni-NPs) embedded in an antiferromagnetic IrMn matrix were investigated. The Ni-NPs of 8.4 nm mean diameter were synthesized by inert gas aggregation. In a second processing step, the Ni-NPs were in situ embedded in IrMn films or SiOx films under ultrahigh vacuum (UHV) conditions. Findings showed that Ni-NPs embedded in IrMn have an exchange bias field HEB = 821 Oe at 10 K, and 50 Oe at 300 K. The extracted value of the exchange energy density is 0.06 mJ m-2 at 10 K, which is in good accordance with the results from multilayered thin film systems. The Ni-NPs embedded in SiOx did not show exchange bias. As expected for this particle size, they are superparamagnetic at T = 300 K. A direct comparison of the Ni-NPs embedded in IrMn or SiOx reveals an increase of the blocking temperature from 210 K to around 400 K. The coercivity of the Ni-NPs exchange coupled to the IrMn matrix at 10 K is 8 times larger than the value for Ni-NPs embedded in SiOx. We studied time-dependent remanent magnetization at different temperatures. The relaxation behavior is described by a magnetic viscosity model which reflects a rather flat distribution of energy barriers. Furthermore, we investigated the effects of different field cooling processes on the magnetic properties of the embedded Ni-NPs. Exchange bias values fit to model calculations which correlate the contribution of the antiferromagnetic IrMn matrix to its grain size.

  9. Exchange bias of Ni nanoparticles embedded in an antiferromagnetic IrMn matrix.

    PubMed

    Kuerbanjiang, Balati; Wiedwald, Ulf; Haering, Felix; Biskupek, Johannes; Kaiser, Ute; Ziemann, Paul; Herr, Ulrich

    2013-11-15

    The magnetic properties of Ni nanoparticles (Ni-NPs) embedded in an antiferromagnetic IrMn matrix were investigated. The Ni-NPs of 8.4 nm mean diameter were synthesized by inert gas aggregation. In a second processing step, the Ni-NPs were in situ embedded in IrMn films or SiOx films under ultrahigh vacuum (UHV) conditions. Findings showed that Ni-NPs embedded in IrMn have an exchange bias field HEB = 821 Oe at 10 K, and 50 Oe at 300 K. The extracted value of the exchange energy density is 0.06 mJ m(-2) at 10 K, which is in good accordance with the results from multilayered thin film systems. The Ni-NPs embedded in SiOx did not show exchange bias. As expected for this particle size, they are superparamagnetic at T = 300 K. A direct comparison of the Ni-NPs embedded in IrMn or SiOx reveals an increase of the blocking temperature from 210 K to around 400 K. The coercivity of the Ni-NPs exchange coupled to the IrMn matrix at 10 K is 8 times larger than the value for Ni-NPs embedded in SiOx. We studied time-dependent remanent magnetization at different temperatures. The relaxation behavior is described by a magnetic viscosity model which reflects a rather flat distribution of energy barriers. Furthermore, we investigated the effects of different field cooling processes on the magnetic properties of the embedded Ni-NPs. Exchange bias values fit to model calculations which correlate the contribution of the antiferromagnetic IrMn matrix to its grain size. PMID:24141385

  10. Hot Corrosion Performance of AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa Coatings Deposited by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Tao, Chong; Wang, Lei; Cheng, Nailiang; Hu, Hengfa; Liu, Yang; Song, Xiu

    2016-04-01

    AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa coatings were deposited on 316L stainless steel substrate using atmospheric plasma spraying, respectively, in order to improve the oxidation and corrosion resistance. The hot corrosion performance of the coatings at 700 and 900 °C were studied, and the detailed microstructures and phase composition of the coatings were analyzed using x-ray diffraction, scanning electron microscope with energy dispersive spectrometer, and transmission electron microscope. The results show that both coatings are structurally featured by slatted layers, consisting of amorphous phase, Cr2O3, Ni3Al, and Al2O3. The hot corrosion resistance of AlO-CrO/NiCoCrAlYTa coating is better than that of AlO/NiCoCrAlYTa coating. This improvement is attributed to lower porosity and more compact Cr2O3 in AlO-CrO/NiCoCrAlYTa coating which performs better than Al2O3 in blocking further inward progress of corrosion and oxidization.

  11. New type of Schottky diode-based Cu-Al-Mn-Cr shape memory material films

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Dere, A.; Mensah-Darkwa, Kwadwo; Al-Ghamdi, Ahmed; Karagoz Genç, Z.; Gupta, R. K.; Yakuphanoglu, F.

    2016-07-01

    Cr-doped CuAlMn shape memory alloys were produced by arc melting method. The effects of Cr content on microstructure and transformation parameters of were investigated. The alloys were characterized by X-ray analysis, optical microscope observations and differential scanning calorimetry measurements. The grain size of the alloys was decreased by the addition of Cr into CuAlMn alloy system. The martensite transformation temperature was shifted both the lower temperature and higher temperature with the addition of chromium. This change was explained on the basis of the change in the thermodynamics such as enthalpy, entropy and activation energy values. The obtained results indicate that the phase transformation temperatures of the CuAlMn alloy system can be controlled by addition of Cr. We fabricated a Schottky barrier diode and observed that ideality factor and barrier height increase with increasing temperature. The diodes exhibited a thermal sensor behavior. This indicates that Schottky diode-based Cu-Al-Mn-Cr shape memory material films can be used as a sensor in high-temperature measurement applications.

  12. Mn-53-Cr-53 Systematics of R-Chondrite NWA 753

    NASA Technical Reports Server (NTRS)

    Jogo, K.; Shih, C-Y.; Reese, Y. D.; Nyquist, L. E.

    2006-01-01

    Chondrules and chondrites are interpreted as objects formed in the early solar system, and it is important to study them in order to elucidate its evolution. Here, we report the study of the Mn-Cr systematics of the R-Chondrite NWA753 and compare the results to other chondrite data. The goal was to determine Cr isotopic and age variations among chondrite groups with different O-isotope signatures. The Mn-53-Cr-53 method as applied to individual chondrules [1] or bulk chondrites [2] is based on the assumption that 53Mn was initially homogeneously distributed in that portion the solar nebula where the chondrules and/or chondrites formed. However, different groups of chondrites formed from regions of different O-isotope compositions. So, different types of chondrites also may have had different initial Mn-53 abundances and/or Cr isotopic compositions. Thus, it is important to determine the Cr isotopic systematics among chondrites from various chondrite groups. We are studying CO-chondrite ALH83108 and Tagish Lake in addition to R-Chondrite NWA753. These meteorites have very distinct O-isotope compositions (Figure 1).

  13. Dielectric function of the ferromagnetic semiconductor CdMnCrTe studied by using spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Hwang, Younghun; Um, Youngho

    2014-11-01

    We describe the pseudo-dielectric function of Cd1- x- y Mn x Cr y Te ferromagnetic semiconductor alloys by using spectroscopic ellipsometry in the 1.0 ~ 6.0 eV spectral range at room temperature. The ellipsometry data include structures that can be attributed to the effects of Cr concentration on the E 0, E 1, E 1 + Δ1, and E 2 critical points. Critical-point (CP) parameters were obtained by fitting standard critical point (SCP) model line shapes to the numerically-calculated second- energy derivatives of ɛ( ω) = ɛ 1( ω) + iɛ 2( ω). The E 0, E 1, E 1 + Δ1, and E 2 energies decreased with Cr content y; this phenomenon is related to the hybridization of the valence and the conduction bands in CdTe with the 3 d states of Mn and Cr.

  14. Mechanism and kinetics of interaction of Fe, Cr, Mo, and Mn atoms with molecular oxygen

    SciTech Connect

    Akhmadov, U.S.; Zaslonko, I.S.; Smirnov, V.N.

    1988-09-01

    By means of resonance atomic absorption in shock waves, rate constants have been measured for the interaction of atoms of a number of transition metals (Fe, Cr, Mo, and Mn) with molecular oxygen. A new method is proposed and used for determining the exponent ..gamma.. in the modified Lambert-Beer law D = element of(ZN)/sup ..gamma../. The bond strength in CrO and MoO molecules has been estimated.

  15. TDNiCr (ni-20Cr-2ThO2) forging studies

    NASA Technical Reports Server (NTRS)

    Filippi, A. M.

    1974-01-01

    Elevated temperature tensile and stress rupture properties were evaluated for forged TDNiCr (Ni-20Cr-2ThO2) and related to thermomechanical history and microstructure. Forging temperature and final annealed condition had pronounced influences on grain size which, in turn, was related to high temperature strength. Tensile strength improved by a factor of 8 as grain size changed from 1 to 150 microns. Stress-rupture strength was improved by a factor of 3 to 5 by a grain size increase from 10 to 1000 microns. Some contributions to the elevated temperature strength of very large grain material may also occur from the development of a strong texture and a preponderance of small twins. Other conditions promoting the improvement of high temperature strength were: an increase of total reduction, forging which continued the metal deformation inherent in the starting material, a low forging speed, and prior deformation by extrusion. The mechanical properties of optimally forged TDNiCr compared favorably to those of high strength sheet developed for space shuttle application.

  16. Point defect processes in neutron irradiated Ni, Fe-15Cr-16Ni and Ti-added modified SUS316SS

    NASA Astrophysics Data System (ADS)

    Horiki, M.; Yoshiie, T.; Sato, K.; Xu, Q.

    2013-05-01

    The defect structures in Ni, Fe-15Cr-16Ni and Ti-added modified SUS316SS (modified SUS316) were examined after neutron irradiation below 0.3 dpa by the Japan Materials Testing Reactor and Belgian Reactor 2 to compare their defect structural evolution. The growth behaviour of interstitial-type dislocation loops (I-loops), stacking fault tetrahedra (SFTs) and voids was found to be quite different among these specimens. I-loops developed at lower temperatures in Ni than in Fe-15Cr-16Ni and modified SUS316, and more swelling occurred in Ni than in Fe-15Cr-16Ni. Finally, there were no voids in modified SUS316. These results were analysed in terms of the I-loop energy. A large discrepancy was found between the analytical results and experimental observations for Ni and modified SUS316, which suggests the formation of unfaulted I-loops directly from collision cascades. The growth of SFTs was detected in Fe-15Cr-16Ni and modified SUS316, and can be explained by a change in the dislocation bias of SFTs resulting from the absorption of alloying elements.

  17. Behavior of Ni, Zn and Cr during low temperature aqueous Fe oxidation processes on Mars

    NASA Astrophysics Data System (ADS)

    Zhao, Yu-Yan S.; McLennan, Scott M.

    2013-05-01

    The behavior of Ni(II), Zn(II) and Cr(III) during the melanterite (FeSO4·7H2O) to hematite (α-Fe2O3) oxidative transformations involving evolution pathways via jarosite ((H3O,K)Fe3(OH)6(SO4)2), schwertmannite (Fe8O8(OH)6(SO4)) and goethite (α-FeOOH) were investigated in an acidic saturated MgSO4 matrix. Results provide important clues about how elevated levels of trace elements are incorporated into the secondary Fe mineralogy assemblages found on Mars and the mechanism for formation of hematitic concretions at Meridiani Planum on Mars. Our results demonstrate that starting at the same concentrations in the initial solution, final amounts of Ni, Zn and Cr in hematite via different pathways are very different. In Path 1 (melanterite → jarosite → hematite), partitioning of Ni, Zn and Cr into jarosite and hematite (formed through dissolution of jarosite) is most likely in the order: Cr > Zn > Ni. In Path 2 (melanterite → schwertmannite → goethite → hematite), schwertmannite and goethite exhibited strong affinities for divalent Ni and Zn. During such a pathway, Ni should accumulate more than Zn by at least a factor of two, and partitioning of Ni, Zn and Cr to the hematite is most likely in the order: Cr > Ni > Zn. Therefore, our results suggest that the high Ni and moderate Zn distribution pattern observed in Meridiani hematitic spherule-bearing samples can be explained best by the schwertmannite-goethite to hematite pathway (Path 2), without need for an additional high Ni source in this region. Although the lack of goethite at Meridiani renders it uncertain if goethite ever served as a precursor to facilitate hematite formation, dehydration of nano-crystalline goethite is thermodynamically favored and cannot be ruled out. On the other hand, if hematitic concretions were formed by dissolution of jarosite (Path 1), then much higher initial Ni/Zn ratios than 1 in initial diagenetic fluids may be necessary to explain the elevated levels of Ni in the spherules

  18. {sup 53}Mn-{sup 53}Cr CHRONOMETRY OF CB CHONDRITE: EVIDENCE FOR UNIFORM DISTRIBUTION OF {sup 53}Mn IN THE EARLY SOLAR SYSTEM

    SciTech Connect

    Yamashita, Katsuyuki; Yamakawa, Akane; Nakamura, Eizo; Maruyama, Seiji

    2010-11-01

    High-precision Cr isotope ratios for chondrules and metal grain separated from CB chondrite Gujba were determined. The {epsilon}{sup 54}Cr values ({epsilon}{sup i}Cr = [({sup i}Cr/{sup 52}Cr){sub sample}/({sup i}Cr/{sup 52}Cr){sub standard} - 1] x 10{sup 4}) for all samples were identical within the analytical uncertainty, with a mean value of +1.29 {+-} 0.02. Uniform {epsilon}{sup 54}Cr signatures of both chondrules and metal grains imply that the Cr isotope systematics of the meteorite was once completely equilibrated. The {epsilon}{sup 53}Cr values of the chondrules and metal grain, on the other hand, display a strong correlation with the {sup 55}Mn/{sup 52}Cr ratio. The {sup 53}Mn/{sup 55}Mn calculated from the slope of the isochron is (3.18 {+-} 0.52) x 10{sup -6}. This corresponds to absolute ages of 4563.7 {+-} 1.2 Ma and 4563.5 {+-} 1.1 Ma using angrites D'Orbigny and LEW 86010, respectively, as time anchors. These ages are consistent with the ages obtained using other short- and long-lived radio nuclides, supporting the uniform distribution of {sup 53}Mn in the early solar nebula.

  19. Structural, thermal and magnetic properties of Ni 1-xMn xFe 2O 4 nanoferrites

    NASA Astrophysics Data System (ADS)

    Shobana, M. K.; Sankar, S.

    2009-07-01

    In this paper, the structural, thermal and magnetic properties of Ni 1-xMn xFe 2O 4 are presented. It is observed that high concentration of Mn 2+ ions into NiFe 2O 4 tends to reduce the particle size. Calcination at 500 °C has resulted in the growth of Ni 1-xMn xFe 2O 4 nanoparticles, but the calcination at 900 °C has led to the evaporation of the majorities of the polyvinyl alcohol. After calcination at 900 °C, crystallographically oriented NiMnFe 2O 4 nanoparticles are formed. These Ni 1-xMn xFe 2O 4 nanoparticles show hysteresis behaviour upon magnetization. On the other hand, saturation magnetization (Ms) values decreases with increasing Mn content in ferrite due to the influence of Mn 2+ ion in the sub lattice.

  20. Room temperature ferromagnetism in Mn-doped NiO nanoparticles

    NASA Astrophysics Data System (ADS)

    Layek, Samar; Verma, H. C.

    2016-01-01

    Mn-doped NiO nanoparticles of the series Ni1-xMnxO (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum.

  1. Effect of Ni content on microwave absorbing properties of MnAl powder

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-zhong; Lin, Pei-hao; Huang, Wei-chao; Pan, Shun-kang; Liu, Ye; Wang, Lei

    2016-09-01

    MnAlNi powder was prepared by the process of vacuum levitation melting and high-energy ball milling, The morphology and phase structure of the powder were analyzed by Scanning Electron Microscope(SEM), X-ray diffraction(XRD) and the effect of the Ni content on microwave absorbing properties of MnAl powder was investigated by an vector network analyzer. The addition of Ni, which improved the microwave absorbing properties of MnAl powder but not changed the composition of Al8Mn5 alloy. The minimum reflectivity of (Al8Mn5)0.95Ni0.05 powder with a coating thickness (d) of 1.8 mm was about -40.8 dB and has better bandwidth effect, the absorbing mechanism of AlMnNi powders on the electromagnetic was related to the electromagnetic loss within the absorbing coatings and the effect of coating thickness on the interference loss of electromagnetic wave.

  2. MODELING OF NI-CR-MO BASED ALLOYS: PART II - KINETICS

    SciTech Connect

    Turchi, P A; Kaufman, L; Liu, Z

    2006-07-07

    The CALPHAD approach is applied to kinetic studies of phase transformations and aging of prototypes of Ni-Cr-Mo-based alloys selected for waste disposal canisters in the Yucca Mountain Project (YMP). Based on a previous study on alloy stability for several candidate alloys, the thermodynamic driving forces together with a newly developed mobility database have been used to analyze diffusion-controlled transformations in these Ni-based alloys. Results on precipitation of the Ni{sub 2}Cr-ordered phase in Ni-Cr and Ni-Cr-Mo alloys, and of the complex P- and {delta}-phases in a surrogate of Alloy 22 are presented, and the output from the modeling are compared with experimental data on aging.

  3. Diffusional creep and creep degradation in the dispersion-strengthened alloy TD-NiCr

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1972-01-01

    Dispersoid-free regions were observed in TD-NiCr (Ni-20Cr-2ThO2) after slow strain rate testing in air from 1145 to 1590 K. Formation of the dispersoid-free regions appears to be the result of diffusional creep. The net effect of this creep is the degradation of TD-NiCr to a duplex microstructure. Degradation is further enhanced by the formation of voids and integranular oxidation in the thoria-free regions. These regions apparently provided sites for void formation and oxide growth since the strength and oxidation resistance of Ni-20Cr is much less than Ni-20Cr-2ThO2. This localized oxidation does not appear to reduce the static load bearing capacity of TD-NiCr since long stress rupture lives were observed even with heavily oxidized microstructures. But this oxidation does significantly reduce the ductility and impact resistance of the material. Dispersoid-free bands and voids were also observed for two other dispersion strengthened alloys, TD-NiCrAl and IN-853. Thus, it appears that diffusional creep is charactertistic of dispersion-strengthened alloys and can play a major role in the creep degradation of these materials.

  4. Bond strength of three dental porcelains to Ni-Cr and Co-Cr-Ti alloys.

    PubMed

    Fernandes Neto, Alfredo Julio; Panzeri, Heitor; Neves, Flavio Domingues; Prado, Ricardo Alves do; Mendonça, Gustavo

    2006-01-01

    Ceramometal bond strength has played an important role for the replacement of gold alloys by nickel-chromium alloys in dentistry. This study evaluated the metal/porcelain bond strength of three ceramic systems (Vita VMK 88, Williams and Duceram) associated with three nickel-chromium alloys (Durabond, Lite Cast B and Resistal P) and one experimental cobalt-chromium-titanium alloy. Thirty cast cylinder specimens (15 mm in height; 6 mm in diameter) were obtained for each alloy, in away that 10 specimens of each alloy were tested with each porcelain. Bond strength was measured with an Emic screw-driven mechanical testing machine by applying parallel shear forces to the specimens until fracture. Kruskal-Wallis and Mann-Whitney U tests were used for statistical analysis of the alloy/ceramic combinations (p<0.05). Resistal P/Duceram had significantly higher bond strength (44.38+/-9.12 MPa) (p<0.05) than the other combinations, except for Co-Cr-Ti alloy/Vita VMK 88 (38.41+/-12.64 MPa). The association of the experimental Co-Cr-Ti alloy with Williams porcelain had significantly higher bond strength (28.20+/-3.86 MPa) than the combination of other alloys with the same porcelain (p<0.05). Based of these results and within the limitations of an in vitro study, it may be concluded that the bond strength of the three ceramic systems to the Ni-Cr and Co-Cr-Ti alloys varied significantly, indicating that metal/ceramic compatibility was very important to the bond strength. PMID:16721460

  5. Electrical manipulation of ferromagnetic NiFe by antiferromagnetic IrMn

    NASA Astrophysics Data System (ADS)

    Tshitoyan, V.; Ciccarelli, C.; Mihai, A. P.; Ali, M.; Irvine, A. C.; Moore, T. A.; Jungwirth, T.; Ferguson, A. J.

    2015-12-01

    We demonstrate that an antiferromagnet can be employed for a highly efficient electrical manipulation of a ferromagnet. In our study, we use an electrical detection technique of the ferromagnetic resonance driven by an in-plane ac current in a NiFe/IrMn bilayer. At room temperature, we observe antidampinglike spin torque acting on the NiFe ferromagnet, generated by an in-plane current driven through the IrMn antiferromagnet. A large enhancement of the torque, characterized by an effective spin-Hall angle exceeding most heavy transition metals, correlates with the presence of the exchange-bias field at the NiFe/IrMn interface. It highlights that, in addition to the strong spin-orbit coupling, the antiferromagnetic order in IrMn governs the observed phenomenon.

  6. 1100 to 1500 K Slow Plastic Compressive Behavior of NiAl-xCr Single Crystals

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Darolia, Ram

    2003-01-01

    The compressive properties of near <001> and <111> oriented NiAl-2Cr single crystals and near <011> oriented NiAl-6Cr samples have been measured between 1100 and 1500 K. The 2Cr addition produced significant solid solution strengthening in NiAl, and the <111> and <001> single crystals possessed similar strengths. The 6Cr crystals were not stronger than the 2Cr versions. At 1100 and 1200 K plastic flow in all three Cr-modified materials was highly dependent on stress with exponents > 10. The <011> oriented 6Cr alloy exhibited a stress exponent of about 8 at 1400 and 1500 K; whereas both <001> and <111> NiAl-2Cr crystals possessed stress exponents near 3 which is indicative of a viscous dislocation glide creep mechanism. While the Cottrell-Jaswon solute drag model predicted creep rates within a factor of 3 at 1500 K for <001>-oriented NiAl-2Cr; this mechanism greatly over predicted creep rates for other orientations and at 1400 K for <001> crystals.

  7. Mechanical and hardness evaluations of Fe-18Cr-18Mn alloys

    SciTech Connect

    Rawers, J.C.; Duttlinger, N.W.

    2008-01-01

    A series of Fe-18Cr-18Mn-N-C alloys was produced and evaluated to determine their mechanical and hardness properties. In one group, different levels of nitrogen and carbon were added to a base composition of Fe-18Cr-18Mn. The base Fe-18Cr-18Mn alloy had a fcc-bcc duplex microstructure. The addition of nitrogen and carbon stabilised the fcc phase. These alloys had increasing room temperature hardness, strength, and failure energy with increasing interstitial concentrations. At cryogenic and elevated temperatures, these alloys had increasing hardness (and by implication, increased strength) with increasing interstitial concentrations. In a second group, different levels of nitrogen and carbon were added to the base Fe-18Cr-18Mn composition to which minor solid solution additions of silicon, molybdenum, and nickel had been added. Minor alloy additions made only nominal improvement to mechanical and hardness properties. Nitrogen remained interstitial. However, these minor solid solution additions reduced carbon solubility resulting in the formation of M23C6 precipitates that, while increasing alloy hardness and strength, greatly reduced fracture toughness. The present study suggests that replacing nickel with manganese in stainless steels results not only in more economical alloys but also in alloys with higher strength and hardness.

  8. Corrosion Behavior of 35CrMn and Q235 Steel in Simulated Acid Rain Conditions

    NASA Astrophysics Data System (ADS)

    Zuo, Xiu-li; Xiang, Bin; Li, Xing; Wei, Zi-dong

    2012-04-01

    Effects of pH value, chloride ion concentration and alternation of wetting and drying time in acid rain on the corrosion of 35CrMn and Q235 steel were investigated through the measurement of polarization curves, electrochemical impedance spectroscopy, x-ray diffraction, and quantum mechanical calculations. The corrosion rate of 35CrMn and Q235 steel increased with decreasing pH values of the simulated acid rain, whereas the corrosion potential of 35CrMn and Q235 steel became more negative. The impedance became higher and the corrosion rate decreased with increasing test time. The dissolution rate of samples increased with chloride ion concentration. Results suggested that the corrosion rate of 35CrMn steel was obviously lower than that of Q235 steel for a more compact rust, α-FeOOH. Quantum chemical calculations further revealed that the increase in corrosion rate of the steel resulted from pitting corrosion caused by the corrosive chloride ion.

  9. Austenite precipitation during tempering in 16Cr-2Ni martensitic stainless steels

    SciTech Connect

    Balan, K.P.; Reddy, A.V.; Sarma, D.S.

    1998-09-04

    The 16Cr-2Ni steel when quenched from austenitizing temperature of 1,323K results in the formation of a complex microstructure consisting of the inherited {delta}-ferrite, martensite and retained austenite with a few undissolved M{sub 23}C{sub 6} carbides. There do not appear to be many reports on tempering behavior of 16Cr-2Ni steel through microstructural characterization using transmission electron microscopy. A comprehensive study is under progress to examine the structure-fracture-property relationship on 16Cr-2Ni steel and the microstructural changes that occur on tempering the steel are dealt with in this paper.

  10. Influence of oxygen partial pressure on the quasi-ternary system Cr-Mn-Ti oxide

    SciTech Connect

    Garcia-Rosales, C.; Schulze, H.A.; Naoumidis, A.; Nickel, H. . Research Centre Juelich)

    1993-11-01

    The quasi-ternary system Cr-Mn-Ti oxide was investigated at 1,000 C under oxygen partial pressures ranging from 0.21 bar to 10[sup [minus]21] bar (1 bar = 10[sup 5] Pa). X-ray diffraction analysis was used to identify phases and determine lattice parameters. The positions of phase boundaries as a function of oxygen partial pressure were measured using the emf method. The spinel MnCr[sub 2]O[sub 4] may be regarded as the most interesting compound in this system. Part of the chromium can be replaced by trivalent titanium at low oxygen partial pressures and by trivalent manganese at high pressures, and the formation of a limited solid solution with the spinel Mn[sub 2]TiO[sub 4] is possible in all cases. As a result, a coherent single-phase spinel region exists over the entire oxygen partial pressure range at 1,000 C.

  11. Microwave irradiated Ni-MnOx/C as an electrocatalyst for methanol oxidation in KOH solution for fuel cell application

    NASA Astrophysics Data System (ADS)

    Hameed, R. M. Abdel

    2015-12-01

    Ni-MnOx/C electrocatalyst was synthesized by the reduction of nickel precursor salt on MnOx/C powder using NaBH4 and the deposition process was motivated with the aid of microwave irradiation. Finer nickel nanoparticles were detected in Ni-MnOx/C using transmission electron microscopy with a lower particle size of 4.5 nm compared to 6 nm in Ni/C. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS) were applied to study the electrocatalytic activity of Ni-MnOx/C for methanol oxidation in 0.5 M KOH solution. The presence of 7.5 wt.% MnOx in Ni-MnOx/C enhanced the oxidation current density by 1.43 times. The catalytic rate constant of methanol oxidation at Ni-MnOx/C was calculated as 3.26 × 103 cm3 mol-1 s-1. An appreciable shift in the maximum frequency at the transition from the resistive to capacitive regions to a higher value in Bode plots of Ni-MnOx/C was shown when compared to Ni/C. It was accompanied by lowered phase angle values. The lowered Warburg impedance value (W) of Ni-MnOx/C at 400 mV confirmed the faster methanol diffusion rate at its surface.

  12. Ni-Cr based dental alloys; Ni release, corrosion and biological evaluation.

    PubMed

    Reclaru, L; Unger, R E; Kirkpatrick, C J; Susz, C; Eschler, P-Y; Zuercher, M-H; Antoniac, I; Lüthy, H

    2012-08-01

    In the last years the dental alloy market has undergone dramatic changes for reasons of economy and biocompatibility. Nickel based alloys have become widely used substitute for the much more expensive precious metal alloys. In Europe the prevalence of nickel allergy is 10-15% for female adults and 1-3% for male adults. Despite the restrictions imposed by the EU for the protection of the general population in contact dermatitis, the use of Ni-Cr dental alloys is on the increase. Some questions have to be faced regarding the safety risk of nickel contained in dental alloys. We have collected based on many EU markets, 8 Ni-Cr dental alloys. Microstructure characterization, corrosion resistance (generalized, crevice and pitting) in saliva and the quantities of cations released in particular nickel and CrVI have been evaluated. We have applied non parametric classification tests (Kendall rank correlation) for all chemical results. Also cytotoxicity tests and an evaluation specific to TNF-alpha have been conducted. According to the obtained results, it was found that their behavior to corrosion was weak but that nickel release was high. The quantities of nickel released are higher than the limits imposed in the EU concerning contact with the skin or piercing. Surprisingly the biological tests did not show any cytotoxic effect on Hela and L929 cells or any change in TNF-alpha expression in monocytic cells. The alloys did not show any proinflammatory response in endothelial cells as demonstrated by the absence of ICAM-1 induction. We note therefore that there is really no direct relationship between the in vitro biological evaluation tests and the physico-chemical characterization of these dental alloys. Clinical and epidemiological studies are required to clarify these aspects. PMID:24364945

  13. Temperature-induced sign change of the magnetic interlayer coupling in Ni/Ni25Mn75/Ni trilayers on Cu3Au(001)

    NASA Astrophysics Data System (ADS)

    Shokr, Y. A.; Erkovan, M.; Wu, C.-B.; Zhang, B.; Sandig, O.; Kuch, W.

    2015-05-01

    We investigated the magnetic interlayer coupling between two ferromagnetic (FM) Ni layers through an antiferromagnetic (AFM) Ni25Mn75 layer and the influence of this coupling on the exchange bias phenomenon. The interlayer coupling energy of an epitaxial trilayer of 14 atomic monolayers (ML) Ni/45 ML Ni25Mn75/16 ML Ni on Cu3Au(001) was extracted from minor-loop magnetization measurements using in-situ magneto-optical Kerr effect. The interlayer coupling changes from ferromagnetic to antiferromagnetic when the temperature is increased above 300 K. This sign change is interpreted as the result of the competition between an antiparallel Ruderman-Kittel-Kasuya-Yosida (RKKY)-type interlayer coupling, which dominates at high temperature, and a stronger direct exchange coupling across the AFM layer, which is present only below the Néel temperature of the AFM layer.

  14. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Tobar, M. J.; Yáñez, A.; Amigó, V.; Candel, J. J.

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed.

  15. Structure, magnetism, and electron-transport properties of Mn2CrGa-based nanomaterials

    NASA Astrophysics Data System (ADS)

    Zhang, Wenyong; Kharel, Parashu; Skomski, Ralph; Valloppilly, Shah; Li, Xingzhong; Sellmyer, David J.

    2016-05-01

    Mn2CrGa in the disordered cubic structure has been synthesized using rapid quenching and subsequent annealing. The cubic phase transforms to a stable tetragonal phase when a fraction of Cr or Ga is replaced by Pt or Al, respectively. All samples are ferrimagnetic with high Curie temperatures (Tc); Mn2CrGa exhibits the highest Tc of about 813 K. The tetragonal samples have appreciable values of magnetocrystalline anisotropy energy, which leads to an increase in coercivity (Hc) that approaches about 10 kOe in the Pt-doped sample. The Hc linearly increases with a decrease of temperature, concomitant with the anisotropy change with temperature. All samples are metallic and show negative magnetoresistance with room-temperature resistivities on the order of 1 mΩcm. The magnetic properties including high Tc and low magnetic moment suggest that these tetragonal materials have potential for spin-transfer-torque-based devices.

  16. Sign reversal of magnetization in Mn substituted SmCrO3

    NASA Astrophysics Data System (ADS)

    Dash, Bibhuti B.; Ravi, S.

    2016-05-01

    Single phase samples of orthorhombic SmCr1-xMnxO3 compounds were prepared for x=0 to 0.50. Analysis of X-ray diffraction patterns shows a systematic increase in lattice parameters with increase in Mn concentration. The phenomenon of magnetization reversal is observed for x=0.10-0.30 samples with a maximum magnetic compensation temperature of 126 K. The mechanism of magnetization reversal is explained by considering the competition between the paramagnetic moments of Mn3+ and Sm3+ ions under the influence of negative internal field due to antiferromagnetically ordered Cr3+ ions and the canted ferromagnetic component of Cr3+ ions. For x≥0.40, the samples exhibit ferromagnetic like behavior.

  17. Realization of magnetostructural coupling by modifying structural transitions in MnNiSi-CoNiGe system with a wide Curie-temperature window.

    PubMed

    Liu, Jun; Gong, Yuanyuan; Xu, Guizhou; Peng, Guo; Shah, Ishfaq Ahmad; Ul Hassan, Najam; Xu, Feng

    2016-01-01

    The magnetostructural coupling between structural and magnetic transitions leads to magneto-multifunctionalities of phase-transition alloys. Due to the increasing demands of multifunctional applications, to search for the new materials with tunable magnetostructural transformations in a large operating temperature range is important. In this work, we demonstrate that by chemically alloying MnNiSi with CoNiGe, the structural transformation temperature of MnNiSi (1200 K) is remarkably decreased by almost 1000 K. A tunable magnetostructural transformation between the paramagnetic hexagonal and ferromagnetic orthorhombic phase over a wide temperature window from 425 to 125 K is realized in (MnNiSi)1-x(CoNiGe)x system. The magnetic-field-induced magnetostructural transformation is accompanied by the high-performance magnetocaloric effect, proving that MnNiSi-CoNiGe system is a promising candidate for magnetic cooling refrigerant. PMID:26979284

  18. Realization of magnetostructural coupling by modifying structural transitions in MnNiSi-CoNiGe system with a wide Curie-temperature window

    PubMed Central

    Liu, Jun; Gong, Yuanyuan; Xu, Guizhou; Peng, Guo; Shah, Ishfaq Ahmad; ul Hassan, Najam; Xu, Feng

    2016-01-01

    The magnetostructural coupling between structural and magnetic transitions leads to magneto-multifunctionalities of phase-transition alloys. Due to the increasing demands of multifunctional applications, to search for the new materials with tunable magnetostructural transformations in a large operating temperature range is important. In this work, we demonstrate that by chemically alloying MnNiSi with CoNiGe, the structural transformation temperature of MnNiSi (1200 K) is remarkably decreased by almost 1000 K. A tunable magnetostructural transformation between the paramagnetic hexagonal and ferromagnetic orthorhombic phase over a wide temperature window from 425 to 125 K is realized in (MnNiSi)1−x(CoNiGe)x system. The magnetic-field-induced magnetostructural transformation is accompanied by the high-performance magnetocaloric effect, proving that MnNiSi-CoNiGe system is a promising candidate for magnetic cooling refrigerant. PMID:26979284

  19. Realization of magnetostructural coupling by modifying structural transitions in MnNiSi-CoNiGe system with a wide Curie-temperature window

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Gong, Yuanyuan; Xu, Guizhou; Peng, Guo; Shah, Ishfaq Ahmad; Ul Hassan, Najam; Xu, Feng

    2016-03-01

    The magnetostructural coupling between structural and magnetic transitions leads to magneto-multifunctionalities of phase-transition alloys. Due to the increasing demands of multifunctional applications, to search for the new materials with tunable magnetostructural transformations in a large operating temperature range is important. In this work, we demonstrate that by chemically alloying MnNiSi with CoNiGe, the structural transformation temperature of MnNiSi (1200 K) is remarkably decreased by almost 1000 K. A tunable magnetostructural transformation between the paramagnetic hexagonal and ferromagnetic orthorhombic phase over a wide temperature window from 425 to 125 K is realized in (MnNiSi)1‑x(CoNiGe)x system. The magnetic-field-induced magnetostructural transformation is accompanied by the high-performance magnetocaloric effect, proving that MnNiSi-CoNiGe system is a promising candidate for magnetic cooling refrigerant.

  20. Anisotropic magnetoresistance and current-perpendicular-to-plane giant magnetoresistance in epitaxial NiMnSb-based multilayers

    NASA Astrophysics Data System (ADS)

    Kwon, B.; Sakuraba, Y.; Sukegawa, H.; Li, S.; Qu, G.; Furubayashi, T.; Hono, K.

    2016-01-01

    We fabricated (001)-oriented C1b-NiMnSb epitaxial films on MgO substrate by a magnetron sputtering system and systematically investigated the structure, magnetic property, and anisotropic magnetoresistance (AMR) effect. NiMnSb film was deposited using a stoichiometric NiMnSb target which has Mn-deficient (Mn ˜ 28.7 at. %) off-stoichiometric composition ratio. We have investigated bulk spin-polarization in NiMnSb films by measuring AMR on the basis of recent study for half-metallic L21-Heusler compounds. Although the negative sign of AMR ratio, which is indicative of half-metallic nature, was observed in the single layer NiMnSb films, the magnitude of AMR ratio (-0.10% at RT) was about half of the largest value reported for half-metallic L21-Heusler compounds. The current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) devices of NiMnSb/Ag/NiMnSb show MR ratio of 13.2% at 10 K and 4.2% at 300 K, which is higher than the previous result for NiMnSb/Cu/NiMnSb CPP-GMR devices [Caballero et al., J. Magn. Magn. Mater. 198-199, 55 (1999)], but much less than the CPP-GMR using L21-Heusler electrodes. The reduction of intrinsic bulk spin-polarization originating from the Mn-deficiency in NiMnSb layer is expected to be the main reason for small MR values.

  1. High Temperature Behavior of Cr3C2-NiCr Coatings in the Actual Coal-Fired Boiler Environment

    NASA Astrophysics Data System (ADS)

    Bhatia, Rakesh; Sidhu, Hazoor Singh; Sidhu, Buta Singh

    2015-03-01

    Erosion-corrosion is a serious problem observed in steam-powered electricity generation plants, and industrial waste incinerators. In the present study, four compositions of Cr3C2-(Ni-20Cr) alloy coating powder were deposited by high-velocity oxy-fuel spray technique on T-91 boiler tube steel. The cyclic studies were performed in a coal-fired boiler at 1123 K ± 10 K (850 °C ± 10 °C). X-ray diffraction, scanning electron microscopy/energy dispersive X-ray analysis and elemental mapping analysis techniques were used to analyze the corrosion products. All the coatings deposited on T-91 boiler tube steel imparted hot corrosion resistance. The 65 pctCr3C2 -35 pct (Ni-20Cr)-coated T-91 steel sample performed better than all other coated samples in the given environment.

  2. Researching for Corrosion-Resistance Performance of Laser-Hybrid Plasma Spraying NiCr-Cr3C2 Coating

    NASA Astrophysics Data System (ADS)

    Li, Shu-qing; Li, Qi-lian; Gong, Shui-li; Wang, Chun

    In this paper, the NiCr-Cr3C2 coating was prepared by laser-hybrid plasma spraying (LHPS)technology, the NSS (Neutral Salt Spraying) test results showed that the LHPS NiCr-Cr3C2 coating had good corrosion-resistance performance comparing with the base material and the APS (air plasma spraying) coating. A SEM (scanning electron microscope) was used to analyze corrosion morphology of the samples, The LHPS coating overcame many shortcomings of the conventional spraying coatings such as poor bonding strength, many porosities, many cracks and so on. LHPS is able to improve the bonding strength as the interfaces are melted and joined by the laser simultaneously with plasma spraying. The coating achieves metallurgy bonding and its microstructure becomes more compact and therefore its corrosion-resistance performance is greatly improved.

  3. Neutron diffraction study of MnNiGa{sub 2}—Structural and magnetic behaviour

    SciTech Connect

    Wang, J. L.; Ma, L.; Wu, G. H.; Hofmann, M.; Avdeev, M.; Kennedy, S. J.; Campbell, S. J.; Md Din, M. F.; Dou, S. X.; Hoelzel, M.

    2014-05-07

    MnNiGa{sub 2} crystallizes in the L21 (Heusler) structure and has a ferromagnetic ordering temperature T{sub C} ∼ 192 K. Rietveld refinement of the neutron diffraction patterns indicates that the Ga atoms occupy the equivalent 8c position, while Mn and Ni share the 4a (0, 0, 0) and 4b (0.5, 0.5, 0.5) sites with a mixed occupancy of Mn and Ni atoms. It is found that that ∼83% of Mn and ∼17% Ni are located at the 4a site while ∼83% of Ni and ∼17% Mn occupy the 4b site. There is no evidence of a magneto-volume effect around T{sub C}. In agreement with this finding, our detailed critical exponent analyses of isothermal magnetization curves and the related Arrott plots confirm that the magnetic phase transition at T{sub C} is second order.

  4. Cytocompatibility evaluation of NiMnSn meta-magnetic shape memory alloys for biomedical applications.

    PubMed

    Guiza-Arguello, Viviana R; Monroe, James A; Karaman, Ibrahim; Hahn, Mariah S

    2016-07-01

    Recently, magnetic shape memory alloys (MSMAs) have emerged as an interesting extension to conventional shape memory alloys (SMAs) due to their capacity to undergo reversible deformation in response to an externally applied magnetic field. Meta-magnetic SMAs (M-MSMAs) are a class of MSMAs that are able to transform magnetic energy to mechanical work by harnessing a magnetic-field induced phase transformation, and thus have the capacity to impose up to 10 times greater stress than conventional MSMAs. As such, M-MSMAs may hold substantial promise in biomedical applications requiring extracorporeal device activation. In the present study, the cytotoxicity and ion release from an Ni50 Mn36 Sn14 atomic percent composition M-MSMA were evaluated using NIH/3T3 fibroblasts. Initial studies showed that the viability of cells exposed to NiMnSn ion leachants was 60 to 67% of tissue culture polystyrene (TCP) controls over 10 to 14 days of culture. This represents a significant improvement in cytocompatibility relative to NiMnGa alloys, one of the most extensively studied MSMA systems, which have been reported to induce 80% cell death in only 48 h. Furthermore, NiMnSn M-MSMA associated cell viability was increased to 80% of TCP controls following layer-by-layer alloy coating with poly(allylamine hydrochloride)/poly(acrylic acid) [PAH/PAA]. Ion release measures revealed that the PAH/PAA coatings decreased total Sn and Mn ion release by 50% and 25%, respectively, and optical microscopy evaluation indicated that the coatings reduced NiMnSn surface oxidation. To our knowledge, this study presents the first cytotoxicity evaluation of NiMnSn M-MSMAs and lays the groundwork for their further biological evaluation. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 853-863, 2016. PMID:25953682

  5. Thermal and structural characterization of Cu-Al-Mn-X (Ti, Ni) shape memory alloys

    NASA Astrophysics Data System (ADS)

    Canbay, C. Aksu; Genc, Z. Karagoz; Sekerci, M.

    2014-05-01

    In this study, the Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys at the range of 10-12 at.% of aluminum and 4-5 at.% manganese were produced by arc melting. We have investigated the effects of the alloying elements on the transformation temperatures, and the structural and the magnetic properties of the quaternary Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys. The evolution of the transformation temperatures was studied by differential scanning calorimetry with different heating and cooling rates. The characteristic transformation temperatures and the thermodynamic parameters were highly sensitive to variations in the aluminum and manganese content, and it was observed that the nickel addition into the Cu-Al-Mn system decreased the transformation temperature although Ti addition caused an increase in the transformation temperatures. The effect of the nickel and the titanium on the thermodynamic parameters such as enthalpy and entropy values was investigated. The structural changes of the samples were studied by X-ray diffraction measurements and by optical microscope observations at room temperature. It is evaluated that the element Ni has been completely soluble in the matrix, and the main phase of the Cu-Al-Mn-Ni sample is martensite, and due to the low solubility of the Ti, the Cu-Al-Mn-Ti sample has precipitates, and a martensite phase at room temperature. The magnetic properties of the Cu-Al-Mn, Cu-Al-Mn-Ni and Cu-Al-Mn-Ti samples were investigated, and the effect of the nickel and the titanium on the magnetic properties was studied.

  6. Chemical separation and mass spectrometry of Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial materials using thermal ionization mass spectrometry.

    PubMed

    Yamakawa, Akane; Yamashita, Katsuyuki; Makishima, Akio; Nakamura, Eizo

    2009-12-01

    A sequential chemical separation technique for Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial silicate rocks was developed for precise and accurate determination of elemental concentration by the isotope dilution method (ID). The technique uses a combination of cation-anion exchange chromatography and Eichrom nickel specific resin. The method was tested using a variety of matrixes including bulk meteorite (Allende), terrestrial peridotite (JP-1), and basalt (JB-1b). Concentrations of each element was determined by thermal ionization mass spectrometry (TIMS) using W filaments and a Si-B-Al type activator for Cr, Fe, Ni, and Zn and a Re filament and silicic acid-H3PO4 activator for Cu. The method can be used to precisely determine the concentrations of these elements in very small silicate samples, including meteorites, geochemical reference samples, and mineral standards for microprobe analysis. Furthermore, the Cr mass spectrometry procedure developed in this study can be extended to determine the isotopic ratios of 53Cr/52Cr and 54Cr/52Cr with precision of approximately 0.05epsilon and approximately 0.10epsilon (1epsilon = 0.01%), respectively, enabling cosmochemical applications such as high precision Mn-Cr chronology and investigation of nucleosynthetic isotopic anomalies in meteorites. PMID:19886654

  7. Electrochemical Testing of Ni-Cr-Mo-Gd Alloys

    SciTech Connect

    T. E. Lister; R. E. Mizia; H. Tian

    2005-10-01

    The waste package site recommendation design specified a boron-containing stainless steel, Neutronit 976/978, for fabrication of the internal baskets that will be used as a corrosion-resistant neutron-absorbing material. Recent corrosion test results gave higher-than-expected corrosion rates for this material. The material callout for these components has been changed to a Ni-Cr-Mo-Gd alloy (ASTM-B 932-04, UNS N06464) that is being developed at the Idaho National Laboratory. This report discusses the results of initial corrosion testing of this material in simulated in-package environments that could contact the fuel baskets after breach of the waste package outer barrier. The corrosion test matrix was executed using the potentiodynamic and potentiostatic electrochemical test techniques. The alloy performance shows low rates of general corrosion after initial removal of a gadolinium-rich second phase that intersects the surface. The high halide-containing test solutions exhibited greater tendencies toward initiation of crevice corrosion.

  8. Deformation and annealing study of NiCrAlY

    NASA Technical Reports Server (NTRS)

    Ebert, L. J.; Trela, D. M.

    1978-01-01

    The elevated temperature properties (tensile and creep) of NiCrALY, a nickel base alloy containing nominally 16% chromium, 4% aluminum, and 2 to 3% yttria (Y2O3) were evaluated and the optimal combination of thermomechanical treatments for maximum creep resistance was determined. Stored strain energy in as-extruded bars (14:1 extrusion ratio) permitted the development of a large grain size in the material when it was annealed at the maximum safe temperature 2450 F (1343 C). With a one-hour anneal at this temperature, the relatively fine grain size of the as-extruded material was changed to one in which the average grain diameter approached 1 mm, and the aspect ratio was about 10. The material was capable of being cold worked (by rolling) in amounts greater than 30% reduction in area. When the cold worked material was given a relaxation treatment, consisting of heating one hour at 1600 F(871 C), and then a high temperature anneal at 2450 F (1343 C) for one hour, both the high temperature strength and the high temperature creep resistance of the material was further enhanced.

  9. Comparative Study on the Corrosion Resistance of Fe-Based Amorphous Metal, Borated Stainless Steel and Ni-Cr-Mo-Gd Alloy

    SciTech Connect

    Lian, Tiangan; Day, Daniel; Hailey, Phillip; Choi, Jor-Shan; Farmer, Joseph

    2007-07-01

    Iron-based amorphous alloy Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4} was compared to borated stainless steel and Ni-Cr-Mo-Gd alloy on their corrosion resistance in various high-concentration chloride solutions. The melt-spun ribbon of this iron-based amorphous alloy have demonstrated a better corrosion resistance than the bulk borated stainless steel and the bulk Ni-Cr-Mo-Gd alloy, in high-concentration chloride brines at temperatures 90 deg. C or higher. (authors)

  10. Anti-wear properties of Cr C and Ni Co alloy coatings as substitutes for conventional nanocrystalline Cr coatings

    NASA Astrophysics Data System (ADS)

    Zeng, Zhixiang; Zhang, Junyan

    2008-09-01

    Nanocrystalline Ni-Co, amorphous Cr-C alloy and nanocrystalline Cr-C coatings were electrodeposited from 'environmentally acceptable' electrolytes as potential substitutes for conventional nanocrystalline Cr coatings electrodeposited from noxious hexavalent chromium. The structure, morphology and hardness of coatings are investigated using a transmission electron microscope, a scanning electronic microscope and a Vickers hardness tester, respectively. Anti-wear properties are tested on a pin-on-plate vibrant wear tester. The correlation between the wear resistance, hardness, brittleness and the lubricated state is investigated. The results show that the wear behaviour of specimens significantly depends on their lubricated state, hardness and brittleness. Under the lubricated sliding condition, abrasive wear is the primary wear mechanism for all specimens. With respect to the abrasive wear mechanism, both the elastic and plastic deformations play important roles during the lubricated sliding process. Thus, the amorphous and nanocrystalline Cr-C alloy coatings, with both high brittleness and high hardness, exhibit a lower wear rate than the conventional Cr and Ni-Co coatings. On the other hand, under the dry sliding condition, the annealed Ni-Co coating, with an excellent compromise between high hardness and toughness, exhibits an abrasive wear mechanism and a relatively low wear rate; in contrast, the brittle Cr-matrix coatings exhibit a severe fatigue/delamination wear mechanism and high wear rate.

  11. Surface Modification of Cr3C2-NiCr Cermet Coatings by Direct Diode Laser Remelting Process

    NASA Astrophysics Data System (ADS)

    Abe, Nobuyuki; Morimoto, Junji; Fukuhra, Shinji; Yamada, Katsuhiro; Tsukamoto, Masahiro

    Thermal spraying technology has been used for the improvement of wear resistance, erosion resistance, heat resistance and corrosion resistance. Corrosion, wear and abrasion resistance of the substrate materials were significantly improved by the paint coatings. These organic paint coatings, however, did not endure high temperatures and did not adhere well. Modern high performance machinery parts subjected to the extremes of temperature and mechanical stress, needs surface protection against high temperature corrosive media, and mechanical wear and tear. Chromium carbide based materials are commonly used for high temperature wear applications. In this study, we treated Cr3C2-NiCr coatings by laser irradiation treatment and examined its hardness in comparison with that formed by HVOF process. Consequently, the average hardness of laser irradiated Cr3C2-NiCr coating was found out to be higher than that of HVOF coating. The laser-treated Cr3C2-35%NiCr coating further improved the solid particle erosion resistance by a factor of almost twice.

  12. Influence of Mn incorporation for Ni on the magnetocaloric properties of rapidly solidified off-stoichiometric NiMnGa ribbons

    NASA Astrophysics Data System (ADS)

    Dey, Sushmita; Singh, Satnam; Roy, R. K.; Ghosh, M.; Mitra, A.; Panda, A. K.

    2016-01-01

    The present investigation addresses the magnetocaloric behaviour in a series of Ni77-xMnxGa23 (x=23, 24, 25, 27 and 29) rapidly solidified alloys prepared in the form of ribbons by melt spinning technique. The approach of the study is to identify the off-stoichiometric composition wherein room temperature magneto-structural transformation is achieved. The alloy chemistry was tailored through Mn incorporation for Ni such that the magnetic and structural transitions were at close proximity to achieve highest entropy value of ΔS equal to 8.51 J Kg-1 K-1 for #Mn24 ribbon measured at an applied field of 3 T. When such transitions are more staggered as in #Mn29 the entropy value of ribbon reduced to as low as 1.61 J Kg-1 K-1. Near room temperature transformations in #Mn24 ribbon have been observed through calorimetric and thermomagnetic evaluation. Reverse martensitic transformation (martensite→autstenite) temperature indicates not only distinct change in the saturation flux density but also an inter-martensitic phase. Microstructural analysis of #Mn24 alloy ribbon revealed structural ordering with the existence of plate morphology evidenced for martensitic phase.

  13. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Pereloma, E. V.; Stohr, R. A.; Miller, M. K.; Ringer, S. P.

    2009-12-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  14. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel using Atom Probe Tomography

    SciTech Connect

    Pereloma, E. V.; Stohr, R A; Miller, Michael K; Ringer, S. P.

    2009-01-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe){sub 3}Ti and (Ni,Fe){sub 3}(Al,Mn) precipitates eventually form after isothermal aging for {approx}60 seconds. The morphology of the (Ni,Fe){sub 3}Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe){sub 3}(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe){sub 3}Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  15. Atomic scale study of grain boundary segregation before carbide nucleation in Ni-Cr-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Li, Hui; Xia, Shuang; Liu, Wenqing; Liu, Tingguang; Zhou, Bangxin

    2013-08-01

    tendency and Gibbs free energy of C in Alloy 690 is higher than in 304 SS, due to the higher bulk C concentration and the site competition of P atoms which segregate at grain boundary [29,30]. It is imply that the segregation tendency is influenced by the bulk concentration of the segregates. Si atoms slightly segregate at grain boundaries in Alloy 690, but do not segregate at grain boundaries in 304 SS. N and P atoms segregate at grain boundary in 304 SS, and their segregation Gibbs free energy are similar. N atoms may be exhausted by the TiN precipitated in the matrix and can not be observed in the grain boundary of Alloy 690 [19]. Mn atoms deplete at grain boundary in 304 SS. This phenomenon is similar to that of proton irradiation induced segregation in 304 SS [32]. B, C, N, P segregation Gibbs energies are similar both in 304 SS and Alloy 690. B and C atoms segregate at grain boundary both in Alloy 690 and 304 SS, P and N segregate at grain boundary in 304 SS. Si atoms segregate at grain boundary in Alloy 690, but do not segregate at grain boundary in 304 SS. Cr enriches at grain boundary both in Alloy 690 and 304 SS, although carbide does not nucleate. Ni and Fe may segregate, deplete or homogeneously distribute at grain boundary in Alloy 690, but they deplete at grain boundary in 304 SS. C and Cr atoms co-segregate at grain boundaries before carbide nucleation in Alloy 690 and 304 SS. Combination with other results in literatures, the evolution of Cr concentration at grain boundary should be enrichment at grain boundary before carbide nucleation, depletion at grain boundary after carbide precipitation, and healing after obvious growth of carbide. After aging treatment at 500 °C for 0.5 h, the total reduction of grain boundary free energy due to segregation is 27.489 kJ/mol for Alloy 690 and 45.207 kJ/mol for 304.

  16. Spin dependent transport properties of Mn-Ga/MgO/Mn-Ga magnetic tunnel junctions with metal(Mg, Co, Cr) insertion layer

    SciTech Connect

    Liang, S. H.; Tao, L. L.; Liu, D. P. Han, X. F.; Lu, Y.

    2014-04-07

    We report a first principles theoretical investigation of spin polarized quantum transport in Mn{sub 2}Ga/MgO/Mn{sub 2}Ga and Mn{sub 3}Ga/MgO/Mn{sub 3}Ga magnetic tunneling junctions (MTJs) with the consideration of metal(Mg, Co, Cr) insertion layer effect. By changing the concentration of Mn, our calculation shows a considerable disparity in transport properties: A tunneling magnetoresistance (TMR) ratio of 852% was obtained for Mn{sub 2}Ga-based MTJs, however, only a 5% TMR ratio for Mn{sub 3}Ga-based MTJs. In addition, the influence of insertion layer has been considered in our calculation. We found the Co insertion layer can increase the TMR of Mn{sub 2}Ga-based MTJ to 904%; however, the Cr insertion layer can decrease the TMR by 668%; A negative TMR ratio can be obtained with Mg insertion layer. Our work gives a comprehensive understanding of the influence of different insertion layer in Mn-Ga based MTJs. It is proved that, due to the transmission can be modulated by the interfacial electronic structure of insertion, the magnetoresistance ratio of Mn{sub 2}Ga/MgO/Mn{sub 2}Ga MTJ can be improved by inserting Co layer.

  17. Redox Dynamics of Mixed Metal (Mn, Cr, and Fe) Ultrafine Particles

    PubMed Central

    Nico, Peter S.; Kumfer, Benjamin M.; Kennedy, Ian M.; Anastasio, Cort

    2008-01-01

    The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O3, whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e. greater than ∼8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging implying that Mn can mediate oxidation by removal of electrons from other particulate metals. PMID:20046215

  18. Redox Dynamics of Mixed Metal (Mn, Cr, and Fe) Ultrafine Particles

    SciTech Connect

    Nico, Peter S.; Kumfer, Benjamin M.; Kennedy, Ian M.; Anastasio, Cort

    2008-08-01

    The impact of particle composition on metal oxidation state, and on changes in oxidation state with simulated atmospheric aging, are investigated experimentally in flame-generated nanoparticles containing Mn, Cr, and Fe. The results demonstrate that the initial fraction of Cr(VI) within the particles decreases with increasing total metal concentration in the flame. In contrast, the initial Mn oxidation state was only partly controlled by metal loading, suggesting the importance of other factors. Two reaction pathways, one reductive and one oxidative, were found to be operating simultaneously during simulated atmospheric aging. The oxidative pathway depended upon the presence of simulated sunlight and O{sub 3}, whereas the reductive pathway occurred in the presence of simulated sunlight alone. The reductive pathway appears to be rapid but transient, allowing the oxidative pathway to dominate with longer aging times, i.e. greater than {approx}8 hours. The presence of Mn within the particles enhanced the importance of the oxidative pathway, leading to more net Cr oxidation during aging implying that Mn can mediate oxidation by removal of electrons from other particulate metals.

  19. PVD synthesis and high-throughput property characterization of NiFeCr alloy libraries

    SciTech Connect

    Rar, A.; Frafjord, J. J.; Fowlkes, Jason D.; Specht, E. D.; Rack, P. D.; Santella, M. L.; Bei, H.; George, E. P.; Pharr, G. M.

    2004-12-16

    Three methods of alloy library synthesis, thick-layer deposition followed by interdiffusion, composition-spread codeposition and electron-beam melting of thick deposited layers, have been applied to Ni-Fe-Cr ternary and Ni-Cr binary alloys. Structural XRD mapping and mechanical characterization by means of nanoindentation have been used to characterize the properties of the libraries. The library synthesis methods are compared from the point of view of the structural and mechanical information they can provide.

  20. Heat treatment of NiCrFe alloy 600 to optimize resistance to intergranular stress corrosion

    DOEpatents

    Steeves, A.F.; Bibb, A.E.

    A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprises heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cooling the alloy body, and heating the cooled body to a temperature between 1100 to 1500/sup 0/F for about 1 to 30 hours.

  1. Heat treatment of NiCrFe alloy to optimize resistance to intergrannular stress corrosion

    DOEpatents

    Steeves, Arthur F.; Bibb, Albert E.

    1984-01-01

    A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprising heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cool the alloy body, and heat the cooled body to a temperature between 1100.degree. to 1500.degree. F. for about 1 to 30 hours.

  2. Precipitates and Grain Boundary Strength of an Fe-Mn-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Heo, Yoon-Uk; Jang, Jae Hoon; Lee, Hu-Chul

    2012-11-01

    The effect of grain boundary (GB) precipitates on the GB strength of an age-hardened Fe-7.8Mn-8.2Ni alloy was investigated. Premature intergranular fracture was observed after age hardening due to the precipitation of θ-MnNi precipitates at prior austenite grain boundaries. However, the conversion of GB θ precipitates to austenite by a short second aging at 793 K (520 °C) after peak aging at 713 K (440 °C) resulted in a remarkable improvement of GB strength. The result strongly supports the proposition that the weak bonding of GB θ precipitates to the matrix is the main reason for GB embrittlement in age-hardened Fe-Mn-Ni alloys.

  3. Dynamic oxidation behavior of TD-NiCr alloy with different surface pretreatments

    NASA Technical Reports Server (NTRS)

    Young, C. T.; Tenney, D. R.; Herring, H. W.

    1975-01-01

    Oxidation tests of TD-NiCr alloy with different surface pretreatments were conducted in a Mach-5 arc-jet at 1200 C and 0.002 lb/sec flowing air environment. The mechanisms responsible for the observed oxidation behavior are examined. The presence of atomic oxygen in the air stream plays a significant role in determining the oxidation characteristic of the alloy. The rate of Cr2O3 vaporization by formation of volatile CrO3 is greatly enhanced by the flowing conditions. The typical microstructure of oxides formed in the dynamic tests consists of an external layer of NiO with a porous mushroom-type morphology, an intermediate layer of NiO and Cr2O3 oxide mixture, and a continuous inner layer of Cr2O3 in contact with the Cr-depleted alloy substrate. Three basic processes underlying the formation of mushroom-type NiO are identified and discussed. The oxidation rate is determined by the rate of vaporization of NiO. Surface pretreatment has a significant effect on the oxidation behavior of the alloy in the early stage of oxidation, but becomes less important as exposure time increases. Mechanical polishing induces surface recrystallization, but promotes the concurrence of external growth of NiO and internal oxidation of the alloy in the dynamic atmosphere.

  4. High-Power Diode Laser-Treated 13Cr4Ni Stainless Steel for Hydro Turbines

    NASA Astrophysics Data System (ADS)

    Mann, B. S.

    2014-06-01

    The cast martensitic chromium nickel stainless steels such as 13Cr4Ni, 16Cr5Ni, and 17Cr4Ni PH have found wide application in hydro turbines. These steels have adequate corrosion resistance with good mechanical properties because of chromium content of more than 12%. The 13Cr4Ni stainless steel is most widely used among these steels; however, lacks silt, cavitation, and water impingement erosion resistances (SER, CER, and WIER). This article deals with characterizing 13Cr4Ni stainless steel for silt, cavitation, and water impingement erosion; and studying its improved SER, CER, and WIER behavior after high-power diode laser (HPDL) surface treatment. The WIER and CER have improved significantly after laser treatment, whereas there is a marginal improvement in SER. The main reason for improved WIER and CER is due to its increased surface hardness and formation of fine-grained microstructure after HPDL surface treatment. CER and WIER of HPDL-treated 13Cr4Ni stainless steel samples have been evaluated as per ASTM G32-2003 and ASTM G73-1978, respectively; and these were correlated with microstructure and mechanical properties such as ultimate tensile strength, modified ultimate resilience, and microhardness. The erosion damage mechanism, compared on the basis of scanning electron micrographs and mechanical properties, is discussed and reported in this article.

  5. Response of Pistia stratiotes to heavy metals (Cr, Ni, and Zn) and phosphorous.

    PubMed

    Mufarrege, M M; Hadad, H R; Maine, M A

    2010-01-01

    The effects of Cr, Ni, Zn, and P exposure on the root anatomic structure, growth, and chlorophyll a concentration of Pistia stratiotes L. were studied. Plastic aquaria containing 50 g of wet plants and 5 L of pond water added with the contaminant(s) were disposed. The treatments were: (1) Cr, (2) Ni, (3) Zn, (4) P, (5) Cr + Ni + Zn, (6) Cr + Ni + Zn + P, and (7) control. Contaminant additions were done seven times. In each addition, concentrations of 1 mg of metals or 5 mg of P per liter of water were added. Chlorophyll a was an indicator more sensitive to Zn and Cr toxicity than the relative growth rate. Ni and Cr + Ni + Zn treatments were the most toxic ones, in which biomass and the root anatomical parameters (root length, cross-sectional areas [CSAs] of root, stele, and metaxylem vessels) decreased significantly. The addition of P to the treatment with combined metals attenuated the decrease in plant growth and root length, and caused a significant increase in CSAs of total metaxylem vessels, suggesting that P increased the tolerance of P. stratiotes to metals. This fact has important implications for the use of this macrophyte in constructed wetlands for industrial wastewater treatment. PMID:19506937

  6. A comparison of the bonding in Cr(NO)4 and Ni(CO)4

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.; Siegbahn, P. E. M.

    1986-01-01

    The bonding in Cr(NO)4 is very ionic, with about 1.5 electrons donated from the Cr to the NO 2pi orbitals. There is also a NO sigma donation of about 0.5 electrons to the Cr, yielding a net charge of Cr of about 1. A large MCSCF expansion is needed to describe both the ionic and covalent contributions to the Cr 3d-NO 2pi bonding. This bonding is compared to that in the isoelectronic Ni(CO)4.

  7. A comparison of the bonding in Cr(NO)4 and Ni(CO)4

    NASA Astrophysics Data System (ADS)

    Bauschlicher, Charles W., Jr.; Siegbahn, Per E. M.

    1986-09-01

    The bonding in Cr(NO)4 is very ionic, with about 1.5 electrons donated from the Cr to the NO 2π orbitals. There is also a NO σ donation of about 0.5 electrons to the Cr, yielding a net charge on Cr of about 1. A large MCSCF expansion is needed to describe both the ionic and covalent contributions to the Cr 3d-NO 2π bonding. This bonding is compared to that in the isoelectronic Ni(CO)4.

  8. Thermomechanical Processing and Roll Bonding of Tri-Layered Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn Composite

    NASA Astrophysics Data System (ADS)

    Kim, Hobyung; Kang, Gyeong Tae; Hong, Sun Ig

    2016-05-01

    Tri-layered Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn composite was processed by roll bonding and the effect of thermomechanical processing on the mechanical performance and electrical conductivity was studied. Roll-bonded composite exhibited the brief work hardening and subsequent rapid work softening because of the high stored deformation energy, leading to failure at the plastic strain of 8 to 10 pct. The mechanical instability of as-roll-bonded composites was abated by heat treatment (HT) at 723 K (450 °C) and the extended work hardening with enhanced ductility compared to that of the as-roll-bonded composites was observed after HT. The strength and electrical conductivity of clad composite is dependent on the precipitation strengthening of Cu-Cr and recovery softening of Cu-Ni-Zn during post-roll-bonding HT. The increase of roll-bonding temperature enhances the precipitation kinetics and it takes shorter time to reach maximum hardness in Cu-Cr layer during post-roll-bonding HT. The toughness of as-roll-bonded Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn clad composite at 773 K (500 °C) [42 MJ/mm3] is greater than those at 723 K (450 °C) [24 MJ/mm3] and 823 K (550 °C) [38 MJ/mm3]. The maximum toughness [100 MJ/mm3] with the electrical conductivity of 68 pct IACS was obtained in the Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn clad composite roll-bonded at 773 K (500 °C) and subsequently heat-treated at 723 K (450 °C).

  9. Inverse magnetocaloric effect in Mn{sub 2}NiGa and Mn{sub 1.75}Ni{sub 1.25}Ga magnetic shape memory alloys

    SciTech Connect

    Singh, Sanjay Barman, S. R.; Esakki Muthu, S.; Arumugam, S.; Senyshyn, A.; Rajput, P.; Suard, E.

    2014-02-03

    Inverse magnetocaloric effect is demonstrated in Mn{sub 2}NiGa and Mn{sub 1.75}Ni{sub 1.25}Ga magnetic shape memory alloys. The entropy change at the martensite transition is larger in Mn{sub 1.75}Ni{sub 1.25}Ga, and it increases linearly with magnetic field in both the specimens. Existence of inverse magnetocaloric effect is consistent with the observation that magnetization in the martensite phase is smaller than the austenite phase. Although the Mn content is smaller in Mn{sub 1.75}Ni{sub 1.25}Ga, from neutron diffraction, we show that the origin of inverse magnetocaloric effect is the antiferromagnetic interaction between the Mn atoms occupying inequivalent sites.

  10. Magnetic, structural and optical properties of Mn-based and Cr-based diluted magnetic semiconductors and alloys

    NASA Astrophysics Data System (ADS)

    Alsaad, A.

    2009-03-01

    We have implemented supercell approach by using local spin density functional theory for Mn-doped GaN, Mn-doped ScN and the linear muffin-tin orbital method to predict the structural and magnetic properties of these novel diluted magnetic semiconductors and their GaxMn1-xN and ScxMn1-xN alloys. The global energy minimum of MnN is obtained for zinc-blende structure. If the compound is compressed by 6 % the energy minimum corresponds to the NaCl structure in disagreement with the experimentally observed a slightly tetragonally distorted rocksalt structure, known as ? phase. The rocksalt structure of CrN at about 8 % lattice expansion becomes stable in the ferromagnetic (FM) state and has a global minimum energy at a lattice constant of 3.9 å. We have observed an isostructural phase transition for ScxMn1-xN alloys from zince-blende phase to hexagonal phase that occurs at a hydrostatic pressure of 17.5 GPa. Moreover, the structural and optical properties of single crystal CrN/ScN superlattices and Cr1-xScxN alloys are studied in details. We report an isostructural phase transition from wurtzite (w-CrN) to hexagonal (h-ScN) at a hydrostatic pressure of 21 GPa. We have also used first-principles methods to study the electronic, optical and magnetic properties of MnN and MnAs compounds in the hypothetical cubic zinc-blende phase, a phase in which the two MnN and MnAs binaries have the same local environment as that they have in GaMnN and GaMnAs alloys. We show that MnN exhibits antiferromagnetic (AFM) ground state and MnAs adopts ferromagnetic (FM) ground state.

  11. Critical behavior of Y2NiMnO6 double perovskite

    NASA Astrophysics Data System (ADS)

    Nhalil, Hariharan; Nair, Harikrishnan S.; Elizabeth, Suja

    2016-05-01

    Critical behavior of double perovskite Y2NiMnO6 near the second-order ferromagnetic transition is studied. Scaling exponents calculated frommodified Arrot plots are confirmed by Kouvel-Fisher method and satisfy the Widom's scaling relation. The exponents do not follow any conventional theoretical models.β values areconsistent with 3D-Ising model whileδconformsto TCMF and γ valueclosely relates to the 3D-Heisenberg model. Critical exponents are compared with similar R2NiMnO6 double perovskites which shows that a decrease in size of R ion changes exponents from mean-field to the 3D-Ising model.

  12. Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

    SciTech Connect

    Nicholson, Don M; Odbadrakh, Khorgolkhuu; Shassere, Benjamin; Rios, Orlando; Hodges, Jason P; Ludtka, Gerard Michael; Porter, Wallace D; Safa-Sefat, Athena; Rusanu, Aurelian; Brown, Greg; Evans III, Boyd Mccutchen

    2014-01-01

    Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system are explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering method. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy are investigated using differential scanning calorimetry and superconducting quantum interference device. Experiments are performed at the Spallation Neutron Source at Oak Ridge National Laboratory to observe the structural and magnetic phase transformations.

  13. Unoccupied electronic structure of Ni2MnGa ferromagnetic shape memory alloy

    DOE PAGESBeta

    Maniraj, M.; D׳Souza, S. W.; Rai, Abhishek; Schlagel, D. L.; Lograsso, T. A.; Chakrabarti, Aparna; Barman, S. R.

    2015-08-20

    Momentum resolved inverse photoemission spectroscopy measurements show that the dispersion of the unoccupied bands of Ni2MnGa is significant in the austenite phase. Furthermore, in the martensite phase, it is markedly reduced, which is possibly related to the structural transition to an incommensurate modulated state in the martensite phase. Finally, based on the first principle calculations of the electronic structure of Ni–Mn–Ga, we show that the modification of the spectral shape with surface composition is related to change in the hybridization between the Mn 3d and Ni 3d-like states that dominate the unoccupied conduction band.

  14. Unoccupied electronic structure of Ni2MnGa ferromagnetic shape memory alloy

    SciTech Connect

    Maniraj, M.; D׳Souza, S. W.; Rai, Abhishek; Schlagel, D. L.; Lograsso, T. A.; Chakrabarti, Aparna; Barman, S. R.

    2015-08-20

    Momentum resolved inverse photoemission spectroscopy measurements show that the dispersion of the unoccupied bands of Ni2MnGa is significant in the austenite phase. Furthermore, in the martensite phase, it is markedly reduced, which is possibly related to the structural transition to an incommensurate modulated state in the martensite phase. Finally, based on the first principle calculations of the electronic structure of Ni–Mn–Ga, we show that the modification of the spectral shape with surface composition is related to change in the hybridization between the Mn 3d and Ni 3d-like states that dominate the unoccupied conduction band.

  15. Local valence and physical properties of double perovskite Nd2NiMnO6

    NASA Astrophysics Data System (ADS)

    Shi, Chenyang; Hao, Yongmei; Hu, Zhongbo

    2011-06-01

    A polycrystalline double perovskite Nd2NiMnO6 (NNM) has been synthesized through the solid-state reaction method. Powder x-ray diffraction data can be indexed by the space group P21/n. Double magnetization transition temperatures at 105.12 K and 193.04 K are observed from temperature-dependent magnetization curve and can be ascribed to Ni3+-O-Mn3+ and Ni2+-O-Mn4+ superexchange interactions, respectively. The effective magnetic moment, Curie constant C and paramagnetic Curie-Weiss temperature θ are calculated to be 6.023μB/f.u., 4.529(4) emu K mol-1 Oe-1 and 191.1(9) K, respectively. Mixed valence of Mn ion is further evidenced by x-ray photoelectron spectra and the mole ratio of Mn3+/Mn4+ is determined to be 19.53 : 81.47. The dielectric relaxor behaviour is found in NNM and follows the Vogel-Fulcher relationship with Ea = 0.0264 eV, Tf = 283.2 K and f0 = 4.66 × 108 Hz. The delocalized carriers in the semiconducting sample may explain the origin of dielectric relaxation.

  16. The microstructure of near-equiatomic B2/f.c.c. FeNiMnAl alloys

    SciTech Connect

    Baker, I.; Wu, H.; Wu, X.; Miller, M.K.; Munroe, P.R.

    2011-10-15

    A microstructural analysis of two FeNiMnAl alloys, Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20}, was performed by a combination of atom probe tomography and transmission electron microscopy techniques. Although the microstructures of both alloys, which consist of alternating platelets aligned along < 100> of the B2-ordered phase, are similar to B2/b.c.c. two-phase alloys previously observed in the FeNiMnAl system, the two phases present in the current alloys are B2-ordered and f.c.c., with the latter phase being heavily twinned. Very fine ({approx} 5 nm) precipitates, whose chemistry was similar to that of the f.c.c. (Fe, Mn)-rich phase, were found within the B2 (Ni, Al)-rich phase in both alloys. - Highlights: {yields} The microstructures of the novel alloys Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20} were characterized. {yields} Atom probe tomography and transmission electron microscopy were used in the study. {yields} A < 100>-aligned B2-ordered phase and heavily-twinned f.c.c. phase were present. {yields} Very fine (Fe, Mn)-rich precipitates were found within the B2 (Ni, Al)-rich phase.

  17. Enhancing alkaline hydrogen evolution reaction activity through Ni-Mn3O4 nanocomposites.

    PubMed

    Li, Xu; Liu, Peng Fei; Zhang, Le; Zu, Meng Yang; Yang, Yun Xia; Yang, Hua Gui

    2016-08-18

    Developing efficient, stable and cost-effective electrocatalysts towards hydrogen production in alkaline environments is vital to improve energy efficiency for water splitting. In this work, we prepared Ni-Mn3O4 nanocomposites on Ni foam which exhibit an excellent hydrogen evolution reaction catalytic activity with a current density (j) of 10 mA cm(-2) at an overpotential (η) of 91 mV and show good stability in an alkaline medium. PMID:27500290

  18. Diffusional transport during the cyclic oxidation of gamma + beta, Ni-Cr-Al(Y, Zr) alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1988-01-01

    The cyclic oxidation behavior of several cast gamma + beta, Ni-Cr-Al(Y, Zr) alloys and one low-pressure plasma spraying gamma + beta, Ni-Co-Cr-Al(Y) alloy was studied. Cyclic oxidation was found to result in a decreasing Al concentration at the oxide-metal interface due to a high rate of Al consumption coupled with oxide scale cracking and spalling. Diffusion paths plotted on the ternary phase diagram showed higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption and the highest Al content underwent breakaway oxidation following 500 1-hr cycles at 1200 C.

  19. Silicon's role in determining swelling in neutron-irradiated Fe-Cr-Ni-Si alloys

    SciTech Connect

    Sekimura, N. ); Garner, F. A. ); Newkirk, J.W. )

    1991-11-01

    Two silicon-modified alloy series, one based on Fe-15Cr-20Ni and another based on Fe-15Cr-25Ni were irradiated at target temperatures between 399 and 649{degree}C in EBR-II. The influence of silicon on swelling is more complex than previously envisioned and indicates that silicon plays two or more competing roles while in solution. Radiation-induced formation of {gamma}{prime} (Ni{sub 3}Si) precipitates is dependent on silicon and nickel content, as well as temperature. Precipitation of {gamma}{prime} appears to play only a minor role in void formation.

  20. Modeling degradation and failure of Ni-Cr-Al overlay coatings

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1984-01-01

    Degradation of a Ni-16Cr-25Al-0.06Zr overlay coating on a Ni-22Cr substrate was examined after oxidation accompanied by thermal cycling. Concentration/distance profiles were measured in the coating and substrate after various one-hour cycles at 1150 C. A numerical model was developed to simulate coating degradation by simultaneous oxidation and coating/substrate interdiffusion. The validity of the model was confirmed by comparison of predicted and measured concentration/distance profiles. The ability of the model to identify critical system parameters was demonstrated for the case of the initial Al and Cr content of the coating and substrate.

  1. The Microstructure of Near-Equiatomic B2/f.c.c. FeNiMnAl Alloys

    SciTech Connect

    Baker, Ian; Wu, H; Wu, Xiaolan; Miller, Michael K; Munroe, P R

    2011-01-01

    A microstructural analysis of two FeNiMnAl alloys, Fe{sub 30}Ni{sub 20}Mn{sub 30}Al{sub 20} and Fe{sub 25}Ni{sub 25}Mn{sub 30}Al{sub 20}, was performed by a combination of atom probe tomography and transmission electron microscopy techniques. Although the microstructures of both alloys, which consist of alternating platelets aligned along <100> of the B2-ordered phase, are similar to B2/b.c.c. two-phase alloys previously observed in the FeNiMnAl system, the two phases present in the current alloys are B2-ordered and f.c.c., with the latter phase being heavily twinned. Very fine ({approx} 5 nm) precipitates, whose chemistry was similar to that of the f.c.c. (Fe, Mn)-rich phase, were found within the B2 (Ni, Al)-rich phase in both alloys.

  2. HfMnSb2 : A Metal-Ordered NiAs-type Pnictide with a Conical Spin Order.

    PubMed

    Murakami, Taito; Yamamoto, Takafumi; Tassel, Cédric; Takatsu, Hiroshi; Ritter, Clemens; Ajiro, Yoshitami; Kageyama, Hiroshi

    2016-08-16

    The NiAs-type structure is one of the most common structures in solids, but metal order has been almost exclusively limited to chalcogenides. The synthesis of HfMnSb2 is reported with a novel metal-ordered NiAs-type structure. HfMnSb2 undergoes a conical spin order below 270 K, in marked contrast to conventional magnetic order observed in NiAs-type pnictides. We argue that the layered arrangement of Hf and Mn makes it a quasi 2D magnet, where the Mn layers with localized magnetic moments (Mn(2+) ; S=5/2) can interact only through RKKY interactions, instead of metal-metal bonding that is otherwise dominant for typical NiAs-type pnictides. This result suggests that controlling order-disorder in NiAs-type pnictides enables a study of 2D-to-3D crossover behavior in itinerant magnetic system. PMID:27355989

  3. Anomalous magnetic configuration of Mn{sub 2}NiAl ribbon and the role of hybridization in the martensitic transformation of Mn{sub 50}Ni{sub 50−x}Al{sub x} ribbons

    SciTech Connect

    Zhao, R. B.; Zhao, D. W.; Li, G. K.; Ma, L. E-mail: houdenglu@mail.hebtu.edu.cn; Zhen, C. M.; Hou, D. L. E-mail: houdenglu@mail.hebtu.edu.cn; Wang, W. H.; Liu, E. K.; Chen, J. L.; Wu, G. H.

    2014-12-08

    The magnetic configuration of Mn{sub 2}NiAl ribbon has been investigated. In contrast to Ni{sub 2}MnAl, the compound Mn{sub 2}NiAl with considerable disorder does exhibit ferromagnetism and, due to exchange interaction competition, both ferromagnetic and antiferromagnetic moment orientations can coexist between nearest neighbor Mn atoms. This is unexpected in Heusler alloys. Regarding the mechanism of the martensitic transformation in Mn{sub 50}Ni{sub 50−x}Al{sub x}, it is found that increasing the Al content results in an unusual change in the lattice constant, a decrease of the transformation entropy change, and enhancement of the calculated electron localization. These results indicate that the p-d covalent hybridization between Mn (or Ni) and Al atoms gradually increases at the expense of the d-d hybridization between Ni and Mn atoms. This leads to an increased stability of the austenite phase and a decrease of the martensitic transformation temperature. For 11 ≤ x ≤ 14, Mn{sub 50}Ni{sub 50−x}Al{sub x} ferromagnetic shape memory alloys are obtained.

  4. Effect of CeO2 on Cyclic Hot-Corrosion Behavior of Detonation-Gun Sprayed Cr3C2-NiCr Coatings on Ni-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Saladi, Sekar; Menghani, Jyoti; Prakash, Satya

    2015-03-01

    The hot-corrosion behavior of detonation-gun sprayed Cr3C2-NiCr coatings with and without 0.4 wt.% CeO2 additive on Ni-based superalloy inconel-718 is comparatively discussed in the present study. Hot-corrosion studies were carried out at 900 °C for 100 cycles in Na2SO4-60%V2O5 molten salt environment under cyclic heating and cooling conditions on bare and coated superalloys. The thermo-gravimetric technique was used to establish kinetics of hot-corrosion. XRD, FESEM/EDAX, and EDX mapping techniques were used to analyze the corrosion products of bare and coated samples. The results indicate that Cr3C2-NiCr-CeO2-coated superalloy showed better hot-corrosion resistance as compared to bare and Cr3C2-NiCr-coated superalloys. The addition of CeO2 has improved micro-hardness, porosity, and surface roughness values of Cr3C2-NiCr-CeO2 coating. The overall weight gain and parabolic rate constant of Cr3C2-NiCr-CeO2-coated superalloy were found to be lowest in the present study signifying that the addition of CeO2 in Cr3C2-NiCr powder has contributed to the development of adherent and dense oxide scale on the coating at elevated temperature.

  5. Alloying effect of Ni and Cr on irradiated microstructural evolution of type 304 stainless steels

    NASA Astrophysics Data System (ADS)

    Tan, L.; Busby, J. T.

    2013-11-01

    Life extension of the existing nuclear power plants imposes significant challenges to core structural materials that suffer increased fluences. This paper presents the microstructural evolution of a type 304 stainless steel and its variants alloyed with extra Ni and Cr under neutron irradiation at ˜320 °C for up to 10.2 dpa. Similar to the reported data of type 304 variants, a large amount of Frank loops, ultrafine G-phase/M23C6 particles, and limited amount of cavities were observed in the irradiated samples. The irradiation promoted the growth of pre-existing M23C6 at grain boundaries and resulted in some phase transformation to CrC in the alloy with both extra Ni and Cr. A new type of ultrafine precipitates, possibly (Ti,Cr)N, was observed in all the samples, and its amount was increased by the irradiation. Additionally, α-ferrite was observed in the type 304 steel but not in the Ni or Ni + Cr alloyed variants. The effect of Ni and Cr alloying on the microstructural evolution is discussed.

  6. Kinetics of borided 31CrMoV9 and 34CrAlNi7 steels

    SciTech Connect

    Efe, Goezde Celebi; Ipek, Mediha; Ozbek, Ibrahim; Bindal, Cuma

    2008-01-15

    In this study, kinetics of borides formed on the surface of 31CrMoV9 and 34CrAlNi7 steels borided in solid medium consisting of Ekabor II at 850-900-950 deg. C for 2, 4, 6 and 8 h were investigated. Scanning electron microscopy and optical microscopy examinations showed that borides formed on the surface of borided steels have columnar morphology. The borides formed in the coating layer confirmed by X-ray diffraction analysis are FeB, Fe{sub 2}B, CrB, and Cr{sub 2}B. The hardnesses of boride layers are much higher than that of matrix. It was found that depending on process temperature and time the fracture toughness of boride layers ranged from 3.93 to 4.48 MPa m{sup 1/2} for 31CrMoV9 and from 3.87 to 4.40 MPa m{sup 1/2} for 34CrAlNi7 steel. Activation energy, growth rate and growth acceleration of boride layer calculated according to these kinetic studies revealed that lower activation energy results in the fast growth rate and high growth acceleration.

  7. Atomic Mobilities and Interdiffusivities for fcc Ni-Cr-Nb Alloys

    NASA Astrophysics Data System (ADS)

    Xu, Gaochi; Liu, Yajun; Kang, Zhitao

    2016-06-01

    The atomic mobilities and diffusion characteristics for fcc Ni-Cr-Nb alloys are explored by diffusion couples annealed at 1273 K (1000 °C) for 200 hours. The interdiffusion coefficients are extracted from intersection points of two diffusion paths, after which the atomic mobilities of Ni, Cr, and Nb in fcc Ni-Cr-Nb alloys are inversely obtained within the CALPHAD framework with the aid of related thermodynamic descriptions. In order to verify the quality of obtained kinetic parameters so that an accurate Ni-based atomic mobility database can be established, the composition profiles in diffusion couples and the diffusion paths superimposed upon Gibbs triangle are explored, where the experimentally measured and calculated values show good agreement.

  8. The Behavior of Gas Powder Laser Clad NiCrBSi Coatings Under Contact Loading

    NASA Astrophysics Data System (ADS)

    Savrai, R. A.; Makarov, A. V.; Soboleva, N. N.; Malygina, I. Yu.; Osintseva, A. L.

    2016-03-01

    The behavior of NiCrBSi coatings obtained by laser cladding from powders with various chromium, carbon and boron contents has been investigated under contact loading through microindentation using a Vickers indenter and via non-impact cyclic loading as per "sphere-to-surface" contact scheme. The phase composition of the coating containing 0.48% C, 14.8% Cr, 2.1% B is γ + Ni3B + Cr23C6 and that of the coating containing 0.92% C, 18.2% Cr, 3.3% B is γ + Ni3B + Cr7C3 + CrB. The established restrictions of the processes of plastic deformation and cracking for the more heavily alloyed and harder coating under contact fatigue loading are substantially due to its increased ability to deform predominantly in the elastic region under the used cyclic loading conditions. This is indicated by the obtained microindentation data and, therefore, the microindentation method (one-time indentation) can be used to assess the ability of the laser clad NiCrBSi coatings to withstand repeated contact loads.

  9. Synthesis of Bimetallic Ni-Cr Nano-Oxides as Catalysts for Methanol Oxidation in NaOH Solution.

    PubMed

    Gu, Yingying; Luo, Jing; Liu, Yicheng; Yang, Haihong; Ouyang, Ruizhou; Miao, Yuqing

    2015-05-01

    Bimetallic Ni-Cr nano-oxide catalysts were synthesized by thermal decomposition method and were investigated as the anode electrocatalysts for the oxidation of methanol. The catalysts were characterized by X-ray diffraction and transmission electron microscopy. The electroactivity of the catalysts towards methanol oxidation in a solution containing 0.25 M NaOH and 1.0 M MeOH was examined using cyclic voltammetry and chronoamperometry. The results indicate that a mixture of rhombohedral-structured NiO and Cr2O3 nanocrystals generated at the calcination temperature of 500-700 degrees C while octahedral-structured spinel NiCr2O4 formed at higher temperature. The influence of metallic molar ratio on the electrocatalytic performance of the catalysts was studied. The Ni-Cr nano-oxides prepared at comparatively low temperature displayed significantly higher catalytic activity and durability in alkaline solution toward electrooxidation of methanol compared with the pure nano NiO. The results indicate a synergy effect between NiO and Cr2O3 enhancing the electrocatalytic properties of the bimetallic Ni-Cr nano-oxide catalysts. Meanwhile, NiCr2O4 hardly increased the activity and durability of the catalyst. In addition, the Ni-Cr catalyst also exhibited excellent stability and good reproducibility. Therefore, Ni-Cr nano-oxide catalyst may be a suitable and cheap electrocatalyst for methanol oxidation in alkaline medium. PMID:26505000

  10. 53Mn-53Cr dating of aqueously formed carbonates in the CM2 lithology of the Sutter's Mill carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Jilly, Christine E.; Huss, Gary R.; Krot, Alexander N.; Nagashima, Kazuhide; Yin, Qing-Zhu; Sugiura, Naoji

    2014-11-01

    Radiometric dating of secondary minerals can be used to constrain the timing of aqueous alteration on meteoritic parent bodies. Dolomite is a well-documented secondary mineral in CM chondrites, and is thought to have formed by precipitation from an aqueous fluid on the CM parent body within several million years of accretion. The petrographic context of crosscutting dolomite veins indicates that aqueous alteration occurred in situ, rather than in the nebular setting. Here, we present 53Mn-53Cr systematics for dolomite grains in Sutter's Mill section SM51-1. The Mn-Cr isotope data show well-resolved excesses of 53Cr correlated with 55Mn/52Cr ratio, which we interpret as evidence for the in situ decay of radioactive 53Mn. After correcting for the relative sensitivities of Mn and Cr using a synthetic Mn- and Cr-bearing calcite standard, the data yield an isochron with slope corresponding to an initial 53Mn/55Mn ratio of 3.42 ± 0.86 × 10-6. The reported error includes systematic uncertainty from the relative sensitivity factor. When calculated relative to the U-corrected Pb-Pb absolute age of the D'Orbigny angrite, Sutter's Mill dolomites give a formation age between 4564.8 and 4562.2 Ma (2.4-5.0 Myr after the birth of the solar system). This age is contemporaneous with previously reported ages for secondary carbonates in CM and CI chondrites. Consistent carbonate precipitation ages between the carbonaceous chondrite groups suggest that aqueous alteration was a common process during the early stages of parent body formation, probably occurring via heating from internal 26Al decay. The high-precision isochron for Sutter's Mill dolomite indicates that late-stage processing did not reach temperatures that were high enough to further disturb the Mn-Cr isochron.

  11. Defect and solute properties in dilute Fe-Cr-Ni austenitic alloys from first principles

    NASA Astrophysics Data System (ADS)

    Klaver, T. P. C.; Hepburn, D. J.; Ackland, G. J.

    2012-05-01

    We present results of an extensive set of first-principles density functional theory calculations of point defect formation, binding, and clustering energies in austenitic Fe with dilute concentrations of Cr and Ni solutes. A large number of possible collinear magnetic structures were investigated as appropriate reference states for austenite. We found that the antiferromagnetic single- and double-layer structures with tetragonal relaxation of the unit cell were the most suitable reference states and highlighted the inherent instabilities in the ferromagnetic states. Test calculations for the presence and influence of noncollinear magnetism were performed but proved mostly negative. We calculate the vacancy formation energy to be between 1.8 and 1.95 eV. Vacancy cluster binding was initially weak at 0.1 eV for divacancies but rapidly increased with additional vacancies. Clusters of up to six vacancies were studied and a highly stable octahedral cluster and stacking fault tetrahedron were found with total binding energies of 2.5 and 2.3 eV, respectively. The <100> dumbbell was found to be the most stable self-interstitial with a formation energy of between 3.2 and 3.6 eV and was found to form strongly bound clusters, consistent with other fcc metals. Pair interaction models were found to be capable of capturing the trends in the defect cluster binding energy data. Solute-solute interactions were found to be weak in general, with a maximal positive binding of 0.1 eV found for Ni-Ni pairs and maximum repulsion found for Cr-Cr pairs of -0.1 eV. Solute cluster binding was found to be consistent with a pair interaction model, with Ni-rich clusters being the most stable. Solute-defect interactions were consistent with Ni and Cr being modestly oversized and undersized solutes, respectively, which is exactly opposite to the experimentally derived size factors for Ni and Cr solutes in type 316 stainless steel and in the pure materials. Ni was found to bind to the vacancy and

  12. Selective Internal Oxidation as a Mechanism for Intergranular Stress Corrosion Cracking of Ni-Cr-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Capell, Brent M.; Was, Gary S.

    2007-06-01

    The mechanism of selective internal oxidation (SIO) for intergranular stress corrosion cracking (IGSCC) of nickel-base alloys has been investigated through a series of experiments using high-purity alloys and a steam environment to control the formation of NiO on the surface. Five alloys (Ni-9Fe, Ni-5Cr, Ni-5Cr-9Fe, Ni-16Cr-9Fe, and Ni-30Cr-9Fe) were used to investigate oxidation and intergranular cracking behavior for hydrogen-to-water vapor partial pressure ratios (PPRs) between 0.001 and 0.9. The Ni-9Fe, Ni-5Cr, and Ni-5Cr-9Fe alloys formed a uniform Ni(OH)2 film at PPRs less than 0.09, and the higher chromium alloys formed chromium-rich oxide films over the entire PPR range studied. Corrosion coupon results show that grain boundary oxides extended for significant depths (>150 nm) below the sample surface for all but the highest Cr containing alloy. Constant extension rate tensile (CERT) test results showed that intergranular cracking varied with PPR and cracking was more pronounced at a PPR value where nonprotective Ni(OH)2 was able to form and a link between the nonprotective Ni(OH)2 film and the formation of grain boundary oxides is suggested. The observation of grain boundary oxides in stressed and unstressed samples as well as the influence of alloy content on IG cracking and oxidation support SIO as a mechanism for IGSCC.

  13. The effects of reactive-element, ion-implantation-induced amorphous layers on the oxidation of Co-12Cr and Ni-12Cr alloys

    SciTech Connect

    Hampikian, J.M.

    1998-08-01

    Nickel-chromium (Ni-12Cr, wt.%) and cobalt-chromium (Co-12Cr, wt.%) alloys were ion implanted with 150 keV yttrium to fluences that ranged between 2 {times} 10{sup 16} and 1 {times} 0{sup 17} ions/cm{sup 2}. The influence of the implantation on the microstructure of the alloy was determined. The effect of the highest dose implantation on the alloys` oxidation response at 1,000 C, 48 hr was measured. Both alloys contained an amorphous surface phase as a result of this fluence and one of the effects of oxidation was to recrystallize the amorphized alloy in the first few minutes of oxidation. The lower doses of 2 {times} 10{sup 16} ions/cm{sup 2} were sufficient to cause amorphization of both the Ni-12Cr and the Co-12Cr. The implantation reduced the isothermal mass gain by a factor of 25% for the Ni-12Cr, but had a negligible effect on the Co-12Cr alloy. Short-term oxidation of experiments at 600 C showed via transmission electron microscopy that, in the absence of the yttrium implant, the Ni-12Cr alloy forms NiO in the first minute of oxidation and the Co-12Cr alloy forms CoO and CoCr{sub 2}O{sub 4}. The implanted Ni-12Cr, on the other hand (1 {times} 10{sup 17} Y{sup +}/cm{sup 2}), forms recrystallized Ni-Cr, Y{sub 2}O{sub 3}, and NiO in the near-surface region, while the implanted Co-12Cr alloy forms CoO, CoCr{sub 2}O{sub 4}, and a recrystallized intermetallic alloy from the amorphized region.

  14. Aliovalent titanium substitution in layered mixed Li Ni-Mn-Co oxides for lithium battery applications

    SciTech Connect

    Kam, Kinson; Doeff, Marca M.

    2010-12-01

    Improved electrochemical characteristics are observed for Li[Ni1/3Co1/3-yMyMn1/3]O2 cathode materials when M=Ti and y<0.07, compared to the baseline material, with up to 15percent increased discharge capacity.

  15. Magnetic, transport, and magnetocaloric properties of boron doped Ni-Mn-In alloys

    SciTech Connect

    Pandey, S.; Quetz, A.; Aryal, A.; Dubenko, I.; Ali, N.; Rodionov, I. D.; Blinov, M. I.; Titov, I. S.; Prudnikov, V. N.; Granovsky, A. B.; Stadler, S.

    2015-05-14

    The impact of B substitution in Ni{sub 50}Mn{sub 35}In{sub 15−x}B{sub x} Heusler alloys on the structural, magnetic, transport, and parameters of the magnetocaloric effect (MCE) has been studied by means of room-temperature X-ray diffraction and thermomagnetic measurements (in magnetic fields (H) up to 5 T, and in the temperature interval 5–400 K). Direct adiabatic temperature change (ΔT{sub AD}) measurements have been carried out for an applied magnetic field change of 1.8 T. The transition temperatures (T-x) phase diagram has been constructed for H = 0.005 T. The MCE parameters were found to be comparable to those observed in other MCE materials such as Ni{sub 50}Mn{sub 34.8}In{sub 14.2}B and Ni{sub 50}Mn{sub 35}In{sub 14}X (X=In, Al, and Ge) Heusler alloys. The maximum absolute value of ΔT{sub AD} = 2.5 K was observed at the magnetostructural transition for Ni{sub 50}Mn{sub 35}In{sub 14.5}B{sub 0.5}.

  16. Magnetic, transport, and magnetocaloric properties of boron doped Ni-Mn-In alloys

    NASA Astrophysics Data System (ADS)

    Pandey, S.; Quetz, A.; Rodionov, I. D.; Aryal, A.; Blinov, M. I.; Titov, I. S.; Prudnikov, V. N.; Granovsky, A. B.; Dubenko, I.; Stadler, S.; Ali, N.

    2015-05-01

    The impact of B substitution in Ni50Mn35In15-xBx Heusler alloys on the structural, magnetic, transport, and parameters of the magnetocaloric effect (MCE) has been studied by means of room-temperature X-ray diffraction and thermomagnetic measurements (in magnetic fields (H) up to 5 T, and in the temperature interval 5-400 K). Direct adiabatic temperature change (ΔTAD) measurements have been carried out for an applied magnetic field change of 1.8 T. The transition temperatures (T-x) phase diagram has been constructed for H = 0.005 T. The MCE parameters were found to be comparable to those observed in other MCE materials such as Ni50Mn34.8In14.2B and Ni50Mn35In14X (X=In, Al, and Ge) Heusler alloys. The maximum absolute value of ΔTAD = 2.5 K was observed at the magnetostructural transition for Ni50Mn35In14.5B0.5.

  17. Microwave synthesis and electrochemical characterization of Mn/Ni mixed oxide for supercapacitor application

    SciTech Connect

    Prasankumar, T.; Jose, Sujin P.; Ilangovan, R.; Venkatesh, K. S.

    2015-06-24

    Nanostructured Mn/Ni mixed metal oxide was synthesized at ambient temperature by facile microwave irradiation technique. The crystal structure and surface morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. X-ray diffraction analysis confirmed the formation of Mn/Ni mixed oxide in rhombohedral phase and the grain size calculated was found to be 87 nm. The irregular spherical morphology of the prepared sample was exhibited by the SEM images. The characteristic peaks of FTIR at about 630 cm{sup −1} and 749 cm{sup −1} were attributed to the Mn-O and Ni-O stretching vibrations respectively. The presence of both Mn and Ni in the prepared sample was validated by the EDS spectra which in turn confirmed the formation of mixed oxide. Cyclic voltammetry and galvanostatic chargedischarge measurements were employed to investigate the electrochemical performance of the mixed oxide. The cyclic voltammetry curves demonstrated good capacitive performance of the sample in the potential window −0.2V to 0.9V. The charge discharge study revealed the suitability of the prepared mixed oxide for the fabrication of supercapacitor electrode.

  18. Thermomagnetic history dependence of magnetocaloric effect in Ni50Mn34In16

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, M. K.; Sharma, V. K.; Roy, S. B.

    2008-01-01

    A large inverse magnetocaloric effect has been reported to be associated with the austenite to martensite phase transition in Ni50Mn34In16. It is shown here that the magnitude of the observed magnetocaloric effect as well as effective refrigerant capacity depend significantly on the thermo-magnetic history of the sample.

  19. Magnetism-Driven Ferroelectricity in Double Perovskite Y₂NiMnO₆.

    PubMed

    Su, J; Yang, Z Z; Lu, X M; Zhang, J T; Gu, L; Lu, C J; Li, Q C; Liu, J-M; Zhu, J S

    2015-06-24

    We report the discovery of multiferroic behavior in double perovskite Y2NiMnO6. X-ray diffraction shows that the material has a centrosymmetric crystal structure of space group P2(1)/n with Ni(2+)/Mn(4+) ordering. This result is further confirmed by aberration-corrected scanning transmission electron microscopy combined with atomic resolution electron energy loss spectroscopy. The appearance of ferroelectric polarization coincides with the magnetic phase transition (∼67 K), which indicates that the ferroelectricity is driven by magnetism, and this is further confirmed by its strong magnetoelectric (ME) effect. We proposed the origin of the ferroelectricity is associated with the combination of Ni(2+)/Mn(4+) charge ordering and the ↑↑↓↓ spin ordering. When compared with other known magnetic multiferroics, Y2NiMnO6 displays several attractive multiferroic properties, including high polarization (∼145 μC/m(2)), a high multiferroic transition temperature (∼67 K), and strong ME coupling (∼21%). PMID:26017622

  20. In Situ Thermo-magnetic Investigation of the Austenitic Phase During Tempering of a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Bojack, A.; Zhao, L.; Morris, P. F.; Sietsma, J.

    2014-09-01

    The formation of austenite during tempering of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) was investigated using an in situ thermo-magnetic technique to establish the kinetics of the martensite to austenite transformation and the stability of austenite. The austenite fraction was obtained from in situ magnetization measurements. It was found that during heating to the tempering temperature 1 to 2 vol pct of austenite, retained during quenching after the austenitization treatment, decomposed between 623 K and 753 K (350 °C and 480 °C). The activation energy for martensite to austenite transformation was found by JMAK-fitting to be 233 kJ/mol. This value is similar to the activation energy for Ni and Mn diffusion in iron and supports the assumption that partitioning of Ni and Mn to austenite are mainly rate determining for the austenite formation during tempering. This also indicates that the stability of austenite during cooling after tempering depends on these elements. With increasing tempering temperature the thermal stability of austenite is decreasing due to the lower concentrations of austenite-stabilizing elements in the increased fraction of austenite. After cooling from the tempering temperature the retained austenite was further partially decomposed during holding at room temperature. This appears to be related to previous martensite formation during cooling.

  1. In Situ Thermo-magnetic Investigation of the Austenitic Phase During Tempering of a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Bojack, A.; Zhao, L.; Morris, P. F.; Sietsma, J.

    2014-12-01

    The formation of austenite during tempering of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) was investigated using an in situ thermo-magnetic technique to establish the kinetics of the martensite to austenite transformation and the stability of austenite. The austenite fraction was obtained from in situ magnetization measurements. It was found that during heating to the tempering temperature 1 to 2 vol pct of austenite, retained during quenching after the austenitization treatment, decomposed between 623 K and 753 K (350 °C and 480 °C). The activation energy for martensite to austenite transformation was found by JMAK-fitting to be 233 kJ/mol. This value is similar to the activation energy for Ni and Mn diffusion in iron and supports the assumption that partitioning of Ni and Mn to austenite are mainly rate determining for the austenite formation during tempering. This also indicates that the stability of austenite during cooling after tempering depends on these elements. With increasing tempering temperature the thermal stability of austenite is decreasing due to the lower concentrations of austenite-stabilizing elements in the increased fraction of austenite. After cooling from the tempering temperature the retained austenite was further partially decomposed during holding at room temperature. This appears to be related to previous martensite formation during cooling.

  2. Construction of the Magnetic Phase Diagram of FeMn/Ni/Cu(001) Using Photoemission Electron Microscopy

    SciTech Connect

    Wu, J.; Scholl, A.; Arenholz, E.; Hwang, C.; Qiu, Z. Q.

    2011-01-04

    Single crystalline FeMn/Ni bilayer was epitaxially grown on Cu(001) substrate and investigated by photoemission electron microscopy (PEEM). The FeMn and Ni films were grown into two cross wedges to facilitate an independent control of the FeMn (0-20 ML) and Ni (0-20 ML) film thicknesses. The Ni magnetic phases were determined by Ni domain images as a function of the Ni thickness (d{sub Ni}) and the FeMn thickness (d{sub FeMn}). The result shows that as the Ni thickness increases, the Ni film undergoes a paramagnetic-to-ferromagnetic state transition at a critical thickness of d{sub FM} and an in-plane to out-of-plane spin reorientation transition at a thicker thickness d{sub SRT}. The phase diagram shows that both d{sub FM} and d{sub SRT} increase as the FeMn film establishes its antiferromagnetic order.

  3. Mössbauer Investigation of Electrodeposited Sn-Zn, Sn-Cr, Sn-Cr-Zn and Fe-Ni-Cr Coatings

    NASA Astrophysics Data System (ADS)

    Kuzmann, E.; Stichleutner, S.; El-Sharif, M.; Chisholm, C. U.; Sziráki, L.; Homonnay, Z.; Vértes, A.

    2002-06-01

    57Fe and 119Sn CEMS, XRD and electrochemical measurements were used to investigate the effect of the preparation parameters and the components on the structure and phase composition of electrodeposited Fe-Ni-Cr alloys in connection with their corrosion behavior. XRD of the electrodeposits reflect an amorphous-like character. 57Fe CEM spectra of Fe-Ni-Cr electrodeposited samples, prepared in a continuous flow plating plastic circulation cell with variation of current density, electrolyte velocity and temperature, can be evaluated as a doublet associated with a highly disordered paramagnetic solid solution phase. This phase was identified earlier in Fe-Ni-Cr electrodeposits that were prepared by another plating method and contained both ferromagnetic and paramagnetic metastable phases [1]. This is the first time that we have succeeded to prepare Fe-Ni-Cr alloys containing only the metastable paramagnetic phase. The effect of the plating parameters on the structure is also analysed by the quadrupole splitting distribution method. 119Sn CEM spectra of all Sn-containing plated alloys show a broad line envelop which can be decomposed at least into two components. One can be associated with β-tin. The other one can be assigned to an alloy phase. The structure and distribution of microenvironments of these phases depends on the plating parameters especially on the parameters of the reverse pulse applied.

  4. Removal of Cr(VI) from aqueous solutions by adsorption on MnO2.

    PubMed

    Gheju, Marius; Balcu, Ionel; Mosoarca, Giannin

    2016-06-01

    Adsorption of Cr(VI) on MnO2 was investigated with respect to effect of pH, temperature, ionic strength, initial Cr(VI) concentration, co-presence of different anions (HCO3(-), SO4(2-), H2PO4(-), NO3(-) and Cl(-)) and of low molecular weight natural organic materials (LMWNOM) (acetate, oxalate and citrate). The process was rapid during the first 3-5min, reaching equilibrium after one hour. Adsorption decreased with increasing pH, temperature and Cr(VI) initial concentration, and increased with increasing ionic strength. Co-presence of phosphate, sulfate, bicarbonate, citrate and oxalate hindered Cr(VI) adsorption, whereas nitrate, chloride and acetate did not exert any notable influence. The overall order of Cr(VI) adsorption suppression due to co-presence of anions and LMWNOM was H2PO4(-)>HCO3(-)>SO4(2-), and oxalate>citrate, respectively. Highest experimental equilibrium sorption capacity (0.83mgg(-1)) was obtained at 20°C and pH 5.9, while lowest (0.18mgg(-1)) was noticed in the co-presence of H2PO4(-), at 20°C and pH 6.9. Adsorption kinetics was successfully fitted by pseudo-second-order model. Mechanisms for both specific and non-specific adsorption are likely to be involved, while rate-controlling step involved both intra-particle and film diffusion processes. Cr(VI) was strongly bound to MnO2, which makes risks of its subsequent liberation into the environment to be low. PMID:26947189

  5. Thermal evolution of vacancy-type defects in quenched FeCrNi alloys

    NASA Astrophysics Data System (ADS)

    Zhang, C. X.; Cao, X. Z.; Li, Y. H.; Jin, S. X.; Lu, E. Y.; Tian, H. W.; Zhang, P.; Wang, B. Y.

    2015-06-01

    The effect of isochronal annealing on vacancy-type defects in quenched FeCrNi alloys and SUS316 was investigated via positron annihilation technique. Vacancy-type defects clustered and grew with increasing annealing temperatures of up to 523 K and, in FeCrNi alloys, were gradually annihilated with increasing temperature. The annihilation temperature was relatively insensitive to the addition of Mo and nonmetal elements, and after annealing at 673 K, the vacancy-type defects were annihilated and dislocation-type defects were formed in all of the alloys. In addition, due to the formation of Mo-vacancy complexes, the density of defects in the Mo-diluted FeCrNi model alloy was lower than that in the FeCrNi model alloy. The long lifetime of vacancy-type defects in commercial stainless steel SUS316 was smaller than that in the FeCrNi model alloys due to the nonmetal-element-induced change in mobility of the defects. Moreover, the vacancy-type and dislocation-type defects contributed to the S and W parameters of positron annihilation during the entire annealing treatment.

  6. Production of Ni-Cr-Ti-natural fibres composite and investigation of mechanical properties

    SciTech Connect

    Pesmen, G.; Erol, A.

    2015-03-30

    Intermetallic materials such as Ni{sub 2}Ti, Cr{sub 2}Ti are among advanced technology materials that have outstanding mechanical and physical properties for high temperature applications. Especially creep resistance, low density and high hardness properties stand out in such intermetallics. The microstructure, mechanical properties of (%50Ni-%48Cr-%2Ti)-%10Naturel Fibres and (%64Ni-%32Cr-%4Ti)-%10Naturel Fibres powders were investigated using specimens produced by tube furnace sintering at 1000-1200-1400°C temperature. A composite consisting of ternary additions, a metallic phase, Ti,Cr and Ni have been prepared under Ar shroud and then tube furnace sintered. XRD, SEM (Scanning Electron Microscope), were investigated to characterize the properties of the specimens. Experimental results carried out for composition (%64Ni-%32Cr-%4Ti)-%10Naturel at 1400°C suggest that the best properties as 112.09HV and 5,422g/cm{sup 3} density were obtained at 1400°C.

  7. Evolution of cavity microstructure in ion-irradiated 316 SS and Fe-20Ni-15Cr alloy. [Fe-20Ni-15Cr

    SciTech Connect

    Kohyama, A.; Loomis, B.; Ayrault, G.; Igata, N.

    1984-04-01

    The effect of helium implantation schedule on the evolution of the cavity microstructure in 316 SS and Fe-20Ni-15Cr alloy during heavy-ion irradiation was investigated for damage levels up to 100 dpa with three helium injection schedules, i.e., 15 appm He/dpa, 50 appm He/dpa and 15 appm He preinjected prior to Ni/sup +/ ion irradiation. In the case of the dual-ion irradiated specimens, there was a trend towards a saturation of the swelling with increasing damage level that was closely related to the saturation and subsequent decrease of the number density of the small cavities (<8 nm diameter for 316 SS and <4 nm for Fe-20Ni-15Cr) and the dislocation density. The bi-model cavity size distribution that was determined for the Fe-20Ni-15Cr alloy at 40 dpa changed to uni-modal distribution at 65 and 100 dpa. Radiation-induced segregation was high and this was related to the saturation tendency for the swelling.

  8. One-pot synthesis of Mn-doped TiO2 grown on graphene and the mechanism for removal of Cr(VI) and Cr(III).

    PubMed

    Chen, Zengping; Li, Yaru; Guo, Meng; Xu, Fengyun; Wang, Peng; Du, Yu; Na, Ping

    2016-06-01

    Mn-doped TiO2 grown on reduced graphene oxide(rGO) was synthesized by one-pot hydrothermal method and the photocatalytic removal of Cr by the material was investigated under sunlight. The materials were characterized by a combination of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, Brunauer-Emmett-Teller method, UV-vis diffuse reflectance spectra, photoluminescence spectra, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Cr(total) removal efficiency of the material is 97.32% in 30min and 99.02% in 60min under sunlight irradiation, as the initial concentration of Cr(VI) is 20mg/L. The high photocatalytic activity under visible light is considered mainly due to the Mn-doping, and rGO plays an important role in the synergetic effect of adsorption and photocatalysis to sustain the high efficient removal of Cr(VI) and Cr(III). Cr(VI) adsorbed on the surface of rGO is reduced to Cr(III) by photo electrons which are transported through rGO, and the reaction product Cr(III) continues to be adsorbed. The process contributes to the release of abundant photocatalytic sites of Mn-TiO2 and improves photocatalytic efficiency. The excellent adsorption and photocatalytic effect with the explanation of the synergetic mechanism are very useful not only for fundamental research but also for the potential practical applications. PMID:26921512

  9. Critical magnetic transition in TbNi2Mn--magnetization and Mössbauer spectroscopy.

    PubMed

    Wang, J L; Campbell, S J; Kennedy, S J; Zeng, R; Dou, S X; Wu, G H

    2011-06-01

    The structural and magnetic properties of the TbNi(2)Mn(x) series (0.9 ≤ x ≤ 1.10) have been investigated using x-ray diffraction, field- and temperature-dependent AC magnetic susceptibility, DC magnetization (5-340 K; 0-5 T) and (57)Fe Mössbauer spectroscopy (5-300 K). TbNi(2)Mn(x) crystallizes in the MgCu(2)-type structure (space group Fd3m). The additional contributions to the magnetic energy terms from transition-metal-transition-metal interactions (T-T) and rare-earth-transition-metal interactions (R-T) in RNi(2)Mn compounds contribute to their increased magnetic ordering temperatures compared with RNi(2) and RMn(2). Both the lattice constant a and the Curie temperature T(C) exhibit maximal values at the x = 1 composition indicating strong magnetostructural coupling. Analyses of the AC magnetic susceptibility and DC magnetization data of TbNi(2)Mn around the Curie temperature T(C) = 147 K confirm that the magnetic transition is second order with critical exponents β = 0.77 ± 0.12, γ = 1.09 ± 0.07 and δ = 2.51 ± 0.06. These exponents establish that the magnetic interactions in TbNi(2)Mn are long range despite mixed occupancies of Tb and Mn atoms at the 8a site and vacancies. The magnetic entropy - ΔS(M) around T(C) is proportional to (μ(0)H/T(C))(2/3) in agreement with the critical magnetic analyses. The Mössbauer spectra above T(C) are fitted by two sub-spectra in agreement with refinement of the x-ray data while below T(C) three sub-spectra are required to represent the three inequivalent local magnetic environments. PMID:21555840

  10. Exceptional damage-tolerance of a medium-entropy alloy CrCoNi at cryogenic temperatures

    DOE PAGESBeta

    Gludovatz, Bernd; Hohenwarter, Anton; Thurston, Keli V. S.; Bei, Hongbin; Wu, Zhenggang; George, Easo P.; Ritchie, Robert O.

    2016-02-02

    The high-entropy alloys are an intriguing new class of metallic materials that derive their properties not from a single dominant constituent, such as iron in steels, nor from the presence of a second phase, such as in nickel-base superalloys, but rather comprise multi-element systems that crystallize as a single phase, despite containing high concentrations (~20 at.%) of five or more elements with different crystal structures. Indeed, we have recently reported on one such single-phase high-entropy alloy, NiCoCrFeMn, which displays exceptional strength and toughness at cryogenic temperatures. Here which displays unprecedented strength-toughness properties that exceed those of all high-entropy alloys andmore » most multi-phase alloys. With roomtemperature tensile strengths of almost 1 GPa and KJIc fracture-toughness values above 200 MPa.m 1/2 (with crack-growth toughnesses exceeding 300 MPa.m 1/2), the strength, ductility and toughness of the NiCoCr alloy actually improve at cryogenic temperatures to unprecedented levels of strengths above 1.3 GPa, failure strains up to 90% and KJIc values of 275 MPa.m 1/2 (with crackgrowth toughnesses above 400 MPa.m 1/2). These properties appear to result from continuous steady strain hardening, which acts to suppress plastic instability, resulting from pronounced dislocation activity and deformation-induced nano-twinning.« less

  11. Characterization of Cold-Sprayed IN625 and NiCr Coatings

    NASA Astrophysics Data System (ADS)

    Srinivasan, Dheepa; Chandrasekhar, Vighnesh; Amuthan, Ramar; Lau, Y. C.; Calla, Eklavya

    2016-04-01

    Ni-based coatings IN625® and Ni20%Cr were cold sprayed on a low-alloy steel (AISI 4130) substrate, using Helium as the process gas. Dense coatings up to 3-mm thickness were deposited, having a hardness of 500-550 HV. The coatings showed a hardness maximum, with heat treatment, before dropping to a lower value. The coating microstructure revealed two distinct types of regions, comprising grains with a high dislocation density and elongated shear bands having twins. Heat treatment led to 30-50 nm grains in the IN625 coating, and >1-2 μm grains for NiCr. Both coatings showed a compressive residual stress in the as-sprayed condition, which relaxed to a zero residual stress, at 650 °C. The NiCr coatings showed a much higher compressibility, as compared to IN625. The IN625 coatings induced a much larger deformation on the 4130 steel. Overall, while both types of Ni-based alloy coatings showed similarities in terms of hardness and microstructure, they revealed distinct differences in their deformability, thermal stability, and substrate deformation, indicating a different behavior between a binary solid solution (NiCr) as compared to a multielement solid solution (IN625), as elucidated via a detailed characterization of these coatings.

  12. LPE growth of Mn, Ni- and Al-substituted copper ferrite films

    NASA Astrophysics Data System (ADS)

    van der Straten, P. J. M.; Metselaar, R.

    1980-06-01

    Single-crystalline Mn-, Ni-, and Al-substituted copper ferrite films are grown by the LPE method from a PbO-B2O3 flux on (111)-MgO substrates. Solid solutions between copper ferrite and Mn3O4, NiFe2O4, and CuAl2O4 are obtained. The segregation coefficients for Ni and Al are shown to be linearly dependent on the growth temperature. From domain-structure observations and from torque measurements it is concluded that a positive uniaxial anisotropy is present in the copper ferrite films. After stress relief at the deposition temperature a stress develops during cooling to room temperature due to a difference in thermal expansion coefficients of film and substrate. This stress is responsible for the observed anisotropy.

  13. Effect of Chromium and Niobium Doping on the Morphology and Electrochemical Performance of High-Voltage Spinel LiNi(0.5)Mn(1.5)O4 Cathode Material.

    PubMed

    Mao, Jing; Dai, Kehua; Xuan, Minjie; Shao, Guosheng; Qiao, Ruimin; Yang, Wanli; Battaglia, Vincent S; Liu, Gao

    2016-04-13

    Undoped, Cr-doped, and Nb-doped LiMn(1.5)Ni(0.5)O4 (LNMO) is synthesized via a PVP (polyvinylpyrrolidone)-combustion method by calcinating at 1000 °C for 6 h. SEM images show that the morphology of LNMO particles is affected by Cr and Nb doping. Cr doping results in sharper edges and corners and smaller particle size, and Nb doping leads to smoother edges and corners and more rounded and larger particles. The crystal and electron structure is investigated by XRD- and synchrotron-based soft X-ray absorption spectroscopy (sXAS). Cr doping and light Nb doping (LiNb(0.02)Ni(0.49)Mn(1.49)O4) improve the rate performance of LNMO. To explore the reason for rate-performance improvement, we conducted potential intermittent titration technique (PITT) and electrochemical impedance spectroscopy (EIS) tests. The Li(+) chemical diffusion coefficient at different state of charge (SOC) is calculated and suggests that both Cr and light Nb doping speeds up Li(+) diffusion in LNMO particles. The impedance spectra show that both R(SEI) and R(ct) are reduced by Cr and light Nb doping. The cycling performance is improved by Cr or Nb doping, and Cr doping increases both Coulombic efficiency and energy efficiency of LNMO at 1 C cycling. The LiCr(0.1)Ni(0.45)Mn(1.45)O4 remains at 94.1% capacity after 500 cycles at 1 C, and during the cycling, the Coulombic efficiency and energy efficiency remain at over 99.7% and 97.5%, respectively. PMID:27008976

  14. Coordination polymer template synthesis of hierarchical MnCo2O4.5 and MnNi6O8 nanoparticles for electrochemical capacitors electrode

    NASA Astrophysics Data System (ADS)

    Wang, Kuaibing; Xu, Jiangyan; Lu, Aimin; Shi, Ying; Lin, Zixia

    2016-08-01

    Two types of ternary metal oxides, MnCo2O4.5 and MnNi6O8 nanoparticles have been separately synthesized through chemical transformation from the corresponding bimetallic coordination polymer particles precursor under high-heating conditions. Series of electrochemical measurements are performed to examine the MnCo2O4.5 and MnNi6O8 electrodes, and the result shows that MnCo2O4.5 structure, especially for Mn/Co-600, has much higher capacitance than that of MnNi6O8 nanoparticles, indicating MnCo2O4.5 electrode is more suitable for applying in neutral electrolyte system. The Mn/Co-600 electrode exhibits a specific capacitance of 158 F g-1 at 5 mV s-1, good rate capability of 53.8% with a 20 times current density increase, good cycle performance (92.9% capacitance retention after 1000 cycles) and high power density (a specific power of 5760 W kg-1 at 4.0 A g-1) with low charge transfer resistance value of 1.8 Ω.

  15. Ti12.5Zr21V10Cr8.5MnxCo1.5Ni46.5-x AB2-type metal hydride alloys for electrochemical storage application: Part 1. Structural characteristics

    NASA Astrophysics Data System (ADS)

    Bendersky, L. A.; Wang, K.; Levin, I.; Newbury, D.; Young, K.; Chao, B.; Creuziger, A.

    2012-11-01

    The microstructures of a series of AB2-based metal hydride alloys (Ti12.5Zr21V10Cr8.5MnxCo1.5Ni46.5-x) designed to have different fractions of non-Laves secondary phases were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectrometry, and electron backscatter diffraction. The results indicate that the alloys contain a majority of hydrogen storage Laves phases and a minority of fine-structured non-Laves phases. Formation of the phases is accomplished by dendritic growth of a hexagonal C14 Laves phase. The C14 phase is followed by either a peritectic solidification of a cubic C15 Laves phase (low Mn containing alloys) or a C14 phase of different composition (high Mn containing alloys), and finally a B2 phase formed in the interdendritic regions (IDR). The interdendritic regions may then undergo further solid-state transformation into Zr7Ni10-type, Zr9Ni11-type and TiNi-type phases. As the Mn content in the alloy increases, the fraction of the C14 phase increases, whereas the fraction of C15 decreases. In the IDRs when the alloy's Mn content increases the Zr9Ni11 phases and Zr7Ni10 phase fraction first increases and then decreases, while the TiNi-based phase fraction first increases and then stabilized at 0.02. IDR compositions can be generally expressed as (Ti,Zr,V,Cr,Mn,Co)50Ni50, which accounted for 7-10% of the overall alloy volume fraction.

  16. Formation of Hierarchical Structure Composed of (Co/Ni)Mn-LDH Nanosheets on MWCNT Backbones for Efficient Electrocatalytic Water Oxidation.

    PubMed

    Jia, Gan; Hu, Yingfei; Qian, Qinfeng; Yao, Yingfang; Zhang, Shiying; Li, Zhaosheng; Zou, Zhigang

    2016-06-15

    Active, stable, and cost-effective electrocatalysts are attractive alternatives to the noble metal oxides that have been used in water splitting. The direct nucleation and growth of electrochemically active LDH materials on chemically modified MWCNTs exhibit considerable electrocatalytic activity toward oxygen evolution from water oxidation. CoMn-based and NiMn-based hybrids were synthesized using a facile chemical bath deposition method and the as-synthesized materials exhibited three-dimensional hierarchical configurations with tunable Co/Mn and Ni/Mn ratio. Benefiting from enhanced electrical conductivity with MWCNT backbones and LDH lamellar structure, the Co5Mn-LDH/MWCNT and Ni5Mn-LDH/MWCNT could generated a current density of 10 mA cm(-2) at overpotentials of ∼300 and ∼350 mV, respectively, in 1 M KOH. In addition, the materials also exhibited outstanding long-term electrocatalytic stability. PMID:27214293

  17. Fully epitaxial C1b-type NiMnSb half-Heusler alloy films for current-perpendicular-to-plane giant magnetoresistance devices with a Ag spacer

    PubMed Central

    Wen, Zhenchao; Kubota, Takahide; Yamamoto, Tatsuya; Takanashi, Koki

    2015-01-01

    Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. Here, we report fully (001)-epitaxial growth of a high-quality half-metallic NiMnSb half-Heusler alloy films, and their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Ag spacer layers. Fully (001)-oriented NiMnSb epitaxial films with very flat surface and high magnetization were prepared on Cr/Ag-buffered MgO(001) single crystalline substrates by changing the substrate temperature. Epitaxial CPP-GMR devices using the NiMnSb films and a Ag spacer were fabricated, and room-temperature (RT) CPP-GMR ratios for the C1b-type half-Heusler alloy were determined for the first time. A CPP-GMR ratio of 8% (21%) at RT (4.2 K) was achieved in the fully epitaxial NiMnSb/Ag/NiMnSb structures. Furthermore, negative anisotropic magnetoresistance (AMR) ratio and small discrepancy of the AMR amplitudes between RT and 10 K were observed in a single epitaxial NiMnSb film, indicating robust bulk half metallicity against thermal fluctuation in the half-Heusler compound. The modest CPP-GMR ratios could be attributed to interface effects between NiMnSb and Ag. This work provides a pathway for engineering a new class of ordered alloy materials with particular emphasis on spintronics. PMID:26672482

  18. Fully epitaxial C1b-type NiMnSb half-Heusler alloy films for current-perpendicular-to-plane giant magnetoresistance devices with a Ag spacer

    NASA Astrophysics Data System (ADS)

    Wen, Zhenchao; Kubota, Takahide; Yamamoto, Tatsuya; Takanashi, Koki

    2015-12-01

    Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. Here, we report fully (001)-epitaxial growth of a high-quality half-metallic NiMnSb half-Heusler alloy films, and their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Ag spacer layers. Fully (001)-oriented NiMnSb epitaxial films with very flat surface and high magnetization were prepared on Cr/Ag-buffered MgO(001) single crystalline substrates by changing the substrate temperature. Epitaxial CPP-GMR devices using the NiMnSb films and a Ag spacer were fabricated, and room-temperature (RT) CPP-GMR ratios for the C1b-type half-Heusler alloy were determined for the first time. A CPP-GMR ratio of 8% (21%) at RT (4.2 K) was achieved in the fully epitaxial NiMnSb/Ag/NiMnSb structures. Furthermore, negative anisotropic magnetoresistance (AMR) ratio and small discrepancy of the AMR amplitudes between RT and 10 K were observed in a single epitaxial NiMnSb film, indicating robust bulk half metallicity against thermal fluctuation in the half-Heusler compound. The modest CPP-GMR ratios could be attributed to interface effects between NiMnSb and Ag. This work provides a pathway for engineering a new class of ordered alloy materials with particular emphasis on spintronics.

  19. Fully epitaxial C1b-type NiMnSb half-Heusler alloy films for current-perpendicular-to-plane giant magnetoresistance devices with a Ag spacer.

    PubMed

    Wen, Zhenchao; Kubota, Takahide; Yamamoto, Tatsuya; Takanashi, Koki

    2015-01-01

    Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. Here, we report fully (001)-epitaxial growth of a high-quality half-metallic NiMnSb half-Heusler alloy films, and their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Ag spacer layers. Fully (001)-oriented NiMnSb epitaxial films with very flat surface and high magnetization were prepared on Cr/Ag-buffered MgO(001) single crystalline substrates by changing the substrate temperature. Epitaxial CPP-GMR devices using the NiMnSb films and a Ag spacer were fabricated, and room-temperature (RT) CPP-GMR ratios for the C1b-type half-Heusler alloy were determined for the first time. A CPP-GMR ratio of 8% (21%) at RT (4.2 K) was achieved in the fully epitaxial NiMnSb/Ag/NiMnSb structures. Furthermore, negative anisotropic magnetoresistance (AMR) ratio and small discrepancy of the AMR amplitudes between RT and 10 K were observed in a single epitaxial NiMnSb film, indicating robust bulk half metallicity against thermal fluctuation in the half-Heusler compound. The modest CPP-GMR ratios could be attributed to interface effects between NiMnSb and Ag. This work provides a pathway for engineering a new class of ordered alloy materials with particular emphasis on spintronics. PMID:26672482

  20. Calorimetric Investigation of Thermal Stability of 304H Cu (Fe-17.7Cr-9.3Ni-2.95Cu-0.91Mn-0.58Nb-0.24Si-0.1C-0.12N-Wt Pct) Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Tripathy, Haraprasanna; Subramanian, Raju; Hajra, Raj Narayan; Rai, Arun Kumar; Rengachari, Mythili; Saibaba, Saroja; Jayakumar, Tammana

    2016-05-01

    The sequence of phase instabilities that take place in a Fe-17.7Cr-9.3Ni-0.58Nb-2.95Cu-0.12N (wt pct) austenitic stainless steel (304H Cu grade) as a function of temperature has been investigated using dynamic calorimetry. The results obtained from this investigation are supplemented by Thermocalc-based equilibrium and Scheil-Gulliver nonequilibrium solidification simulation. The following phase transformation sequence is found upon slow cooling from liquid: L → L + γ → L + γ + MX → γ + MX + δ → γ +MX + M23C6 → γ + MX + M23C6 + Cu. Under slow cooling, the solidification follows austenite + ferrite (AF) mode, which is in accordance with Thermocalc prediction and Scheil-Gulliver simulation. However, higher cooling rates result in skeletal δ-ferrite formation, due to increased segregation tendency of Nb and Cr to segregate to interdendritic liquid. The solidification mode is found to depend on combined Nb + Cu content. Experimental estimates of enthalpy change associated with melting and secondary phase precipitation are also obtained. In addition a semi-quantitative study on the dissolution kinetics of M23C6 type carbides has also been investigated. The standard solution treatment at 1413 K (1140 °C) is found to be adequate to dissolve both Cu and M23C6 into γ-austenite; but the complete dissolution of MX type carbonitrides occurs near the melting region.

  1. Hierarchical Electrospun and Cooperatively Assembled Nanoporous Ni/NiO/MnOx/Carbon Nanofiber Composites for Lithium Ion Battery Anodes.

    PubMed

    Bhaway, Sarang M; Chen, Yu-Ming; Guo, Yuanhao; Tangvijitsakul, Pattarasai; Soucek, Mark D; Cakmak, Miko; Zhu, Yu; Vogt, Bryan D

    2016-08-01

    A facile method to fabricate hierarchically structured fiber composites is described based on the electrospinning of a dope containing nickel and manganese nitrate salts, citric acid, phenolic resin, and an amphiphilic block copolymer. Carbonization of these fiber mats at 800 °C generates metallic Ni-encapsulated NiO/MnOx/carbon composite fibers with average BET surface area (150 m(2)/g) almost 3 times higher than those reported for nonporous metal oxide nanofibers. The average diameter (∼900 nm) of these fiber composites is nearly invariant of chemical composition and can be easily tuned by the dope concentration and electrospinning conditions. The metallic Ni nanoparticle encapsulation of NiO/MnOx/C fibers leads to enhanced electrical conductivity of the fibers, while the block copolymers template an internal nanoporous morphology and the carbon in these composite fibers helps to accommodate volumetric changes during charging. These attributes can lead to lithium ion battery anodes with decent rate performance and long-term cycle stability, but performance strongly depends on the composition of the composite fibers. The composite fibers produced from a dope where the metal nitrate is 66% Ni generates the anode that exhibits the highest reversible specific capacity at high rate for any composition, even when including the mass of the nonactive carbon and Ni(0) in the calculation of the capacity. On the basis of the active oxides alone, near-theoretical capacity and excellent cycling stability are achieved for this composition. These cooperatively assembled hierarchical composites provide a platform for fundamentally assessing compositional dependencies for electrochemical performance. Moreover, this electrospinning strategy is readily scalable for the fabrication of a wide variety of nanoporous transition metal oxide fibers. PMID:27399605

  2. Spectroscopy and atomic physics of highly ionized Cr, Fe, and Ni for tokamak plasmas

    NASA Technical Reports Server (NTRS)

    Feldman, U.; Doschek, G. A.; Cheng, C.-C.; Bhatia, A. K.

    1980-01-01

    The paper considers the spectroscopy and atomic physics for some highly ionized Cr, Fe, and Ni ions produced in tokamak plasmas. Forbidden and intersystem wavelengths for Cr and Ni ions are extrapolated and interpolated using the known wavelengths for Fe lines identified in solar-flare plasmas. Tables of transition probabilities for the B I, C I, N I, O I, and F I isoelectronic sequences are presented, and collision strengths and transition probabilities for Cr, Fe, and Ni ions of the Be I sequence are given. Similarities of tokamak and solar spectra are discussed, and it is shown how the atomic data presented may be used to determine ion abundances and electron densities in low-density plasmas.

  3. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33 Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approximately 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  4. Corrosion resistance of stainless steels and high Ni-Cr alloys to acid fluoride wastes

    SciTech Connect

    Smith, H.D.; Mackey, D.B.; Pool, K.H. ); Schwenk, E.B. )

    1992-04-01

    TRUEX processing of Hanford Site waste will utilize potentially corrosive acid fluoride processing solutions. Appropriate construction materials for such a processing facility need to be identified. Toward this objective, candidate stainless steels and high Ni-Cr alloys have been corrosion tested in simulated acid fluoride process solutions at 333K. The high Ni-Cr alloys exhibited corrosion rates as low as 0.14 mm/y in a solution with an HF activity of about 1.2 M, much lower than the 19 to 94 mm/y observed for austenitic stainless steels. At a lower HF activity (about 0.008 M), stainless steels display delayed passivation while high Ni-Cr alloys display essentially no reaction.

  5. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approx. 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  6. Synthesis of NiCr2O4 spinel coatings with high emissivity by plasma spraying

    NASA Astrophysics Data System (ADS)

    Zhu, Zhen-Qi; Cheng, Xu-Dong; Ye, Wei-Ping; Min, Jie

    2012-03-01

    Air plasma spraying (APS) was used to produce high emissivity coatings with a NiCr2O4 spinel structure. The relationship between the emissivity and the crystal structure was investigated. X-ray diffraction (XRD) analyses show that NiCr2O4 spinel has been fabricated with the space group Fd3 m. Scanning electron microscope (SEM) photographs show that the coating consists of a laminated structure with homogeneous grains and high porosity because of the unique feature of plasma spraying. The emissivity measurement and Fourier transformation infrared radiation (FT-IR) spectra show that NiCr2O4 has a high emissivity of about 0.91 because of its special spinel structure. APS is a suitable method to produce high emissivity coatings.

  7. Corrosion and oxidation properties of NiCr coatings sprayed in presence of gas shroud system

    NASA Astrophysics Data System (ADS)

    Morks, M. F.; Berndt, C. C.

    2010-04-01

    The oxidation of a NiCr bond coat during air plasma spraying was controlled by designing a gas shroud system attached to the plasma torch nozzle. Two nozzles, termed as "normal" and "high-speed" nozzles examined the effect of nozzle internal design on the microstructure and phase structure of coatings. X-ray diffraction and SEM morphologies showed that the shroud system reduced the oxidation of NiCr particles during the spray process. Compared with conventional air plasma spraying, the argon gas shroud reduced the coating hardness because the volume fraction of partially melted particles increased. The high-speed nozzle reduced the oxidation and hardness of NiCr coatings due to the increase of partially melted particles in the coatings.

  8. Stochastic jumps of magnetization in [Mn{(R/S)-pn}]2[Mn{(R/S)-pn}2(H2O)][Cr(CN)6]2 molecular magnet

    NASA Astrophysics Data System (ADS)

    Kirman, M. V.; Talantsev, A. D.; Koplak, O. V.; Morgunov, R. B.

    2015-03-01

    Series of stochastic jumps of the magnetic moment (up to five individual jumps) have been observed at the demagnetization of single crystals of [Mn{(R/S)-pn}]2[Mn{(R/S)-pn}2(H2O)][Cr(CN)6]2 molecular magnet in a narrow range of magnetic fields near the coercive force ( H c = 7.5 Oe). The magnetic field at which jumps of the magnetization arise decreases with an increase in the temperature.

  9. Searching for 0+ states in 50Cr: Implications for the superallowed β decay of 50Mn

    NASA Astrophysics Data System (ADS)

    Leach, K. G.; Garrett, P. E.; Ball, G. C.; Bender, P. C.; Bildstein, V.; Brown, B. A.; Burbadge, C.; Faestermann, T.; Hadinia, B.; Holt, J. D.; Laffoley, A. T.; Jamieson, D. S.; Jigmeddorj, B.; Radich, A. J.; Rand, E. T.; Stroberg, S. R.; Svensson, C. E.; Towner, I. S.; Wirth, H.-F.

    2016-07-01

    A 52Cr(p ,t )50Cr two-neutron pickup reaction was performed using the Q3D magnetic spectrograph at the Maier-Leibnitz-Laboratorium in Garching, Germany. Excited states in 50Cr were observed up to an excitation energy of 5.3 MeV. Despite significantly increased sensitivity and resolution over previous work, no evidence of the previously assigned first excited 0+ state was found. As a result, the 02+ state is reassigned at an excitation energy of Ex=3895.0 (5 ) keV in 50Cr. This reassignment directly impacts direct searches for a nonanalog Fermi β+ decay branch in 50Mn. These results also show better systematic agreement with the theoretical predictions for the 0+ state spectrum in 50Cr using the same formalism as the isospin-symmetry-breaking correction calculations for superallowed nuclei. The experimental data are also compared to ab-initio shell-model predictions using the IM-SRG formalism based on N N and 3 N forces from chiral-EFT in the p f -shell for the first time.

  10. Understanding the role of structural disorder on spin polarization in CeMnNi4 using XAFS

    SciTech Connect

    Lahiri, D.; Khalid, S.; Modak, P.; Raychaudhuri, P.; Dhar, S.K.; Sharma, S.M.

    2010-02-03

    The role of disorder on ferromagnetism has generally been detrimental. We show how Mn-Ni antisite disorder enhances polarization in CeMnNi{sub 4}. The disorder is determined to be 6% by x-ray absorption fine structure. The electronic structure of pure CeMnNi{sub 4} is pseudo-half-metallic. Site exchange alters the near neighbor bond parameters and modifies the density of states favorably, increasing the polarization (obtained by first-principles calculations) from 13 to 47% (experimental {approx}66%).

  11. Luminescence Dynamics of Cr2+ in CdTe and Cd0.55Mn0.45Te

    NASA Astrophysics Data System (ADS)

    Bluiett, A.; Hommerich, U.; Seo, J. T.; Shah, R.; Trivedi, S. B.; Kutcher, S. W.; Chen, R. J.; Wang, C. C.; Zong, H.

    2001-04-01

    Cr^2+ in tetrahedrally coordinated CdTe and Cd_0.55Mn_0.45Te crystals are under investigation as potential host materials for tunable, mid-infrared (MIR) lasers. The small crystal field splitting of the free ion energy levels of Cr^2+ induces absorption (1900nm) and stokes shifted emission (2000nm-3000nm) bands in the MIR. Also, the relatively large ionic mass and tetrahedral environment of Cr^2+ in CdTe and Cd_0.55Mn_0.45Te have shown that the luminescence efficiency at room temperature is approximately 72100luminescence lifetime decreases rapidly, which suggest that the effects of nonradiative decay increases. The decay dynamics of Cr^2+ in CdTe and Cd_0.55Mn_0.45Te will be described with the model of Struck and Fonger for the non-radiative decay rate.

  12. Low temperature spin dynamics in Cr7Ni-Cu-Cr7Ni coupled molecular rings

    SciTech Connect

    Bordonali, L; Furukawa, Y; Mariani, M; Sabareesh, K P; Garlatti, E; Carretta, S; Lascialfari, A; Timco, G; Winpenny, R E; Borsa, F

    2014-05-07

    Proton Nuclear Magnetic Resonance (NMR) relaxation measurements have been performed down to very low temperature (50 mK) to determine the effect of coupling two Cr7 Ni molecular rings via a Cu2+ ion. No difference in the spin dynamics was found from nuclear spin lattice relaxation down to 1.5 K. At lower temperature, the 1H-NMR line broadens dramatically indicating spin freezing. From the plot of the line width vs. magnetization, it is found that the freezing temperature is higher (260 mK) in the coupled ring with respect to the single Cr7 Ni ring (140 mK).

  13. Neutron cross section covariances in the resonance region: 52Cr, 56Fe, 58Ni

    SciTech Connect

    Oblozinsky, P.; Cho, Y.-S.; Mattoon, C.M.; Mughabghab, S.F.

    2010-08-03

    We evaluated covariances for neutron capture and elastic scattering cross sections on major structural materials, {sup 52}Cr, {sup 56}Fe and {sup 58}Ni, in the resonance region which extends beyond 800 keV for each of them. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. The data of most interest for AFCI applications, elastic scattering cross section uncertainties at energies above about few hundred keV, are on the level of about 12% for {sup 52}Cr, 7-8% for {sup 56}Fe and 5-6% for {sup 58}Ni.

  14. Adherent Al2O3 scales formed on undoped NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1987-01-01

    Changes in the spalling behavior of Al2O3 scales formed on an undoped NiCrAl alloy are described. Two samples of Ni-15Cr-13Al (wt pct), one a control and the other sanded, were subjected to 25 oxidation cycles. It is observed that adherent scales formed on the sanded sample; however, the control sample had speckled, spalled scales. The data reveal that the adherent scales are caused by repeated removal of surface layers after each oxidation cycle. It is determined that interfacial segregation of sulfur influences spallation and sulfur removal increases bonding. The effect of moisture on scale adhesions is investigated.

  15. Magnetic Structure of NiCr2O4 Studied by Neutron Scattering and Magnetization Measurements

    NASA Astrophysics Data System (ADS)

    Tomiyasu, Keisuke; Kagomiya, Isao

    2004-09-01

    The magnetic ordering of the normal spinel ferrimagnet NiCr2O4 below TC = 74 K was reinvestigated by neutron scattering and magnetization measurements on a powder specimen. We found another magnetic transition at TS = 31 K besides TC in both experiments. The ordering of a ferrimagnetic (longitudinal) component and that of an antiferromagnetic (transverse) component occur at TC and TS, separately. A new magnetic structure model of NiCr2O4 below TS with a spontaneous magnetization of about 0.3 μB/formula is proposed based on experimental neutron scattering intensity.

  16. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Douglass, D. L.; Nasrallah, M.

    1974-01-01

    The investigation reported included a determination of the optimum composition of a Ni-Cr-Al ternary alloy with respect to oxidation resistance and minimum film-spalling tendencies. Yttrium and thorium in small amounts were added to the ternary alloy and an investigation of the oxidation mechanism and the oxide scale adherence was conducted. It was found that the oxidation mechanism of Ni-Cr-Al ternary alloys depends upon the composition of the alloy as well as the time, oxygen pressure, and temperature of oxidation.

  17. Mechanical properties and strengthening of a Ni-25Mo-8Cr alloy containing Ni{sub 2}(Mo,Cr) precipitates

    SciTech Connect

    Kumar, M.; Vasudevan, V.K.

    1996-12-01

    The mechanical properties and mechanisms of deformation and strengthening of Haynes Alloy 242{sup tm}, a nominal Ni-25Mo-8Cr (in wt%) containing Ni{sub 2}(Mo,Cr) precipitates in a face-centered cubic matrix, are reported. Both solution treated, as well as aged samples (550--750 C, 1--1,200 h) were deformed to permanent strains of 1 and 6% in compression and to failure in tension. The deformation structures were observed by transmission electron microscopy. A two-fold increase in strength and tremendous strain hardening are observed as the short-range (SRO) to long-range ordering (LRO) transformation proceeds, although ductility remains high even in well-aged samples. Major contribution to strengthening and strain hardening comes from the precipitation of a high volume fraction of Ni{sub 2}(Mo,Cr) precipitates, with hardening in the solution treated samples and those aged for short periods being associated with the presence of SRO in the matrix. A transition in deformation mode, from glide of unit dislocations in planar arrays to profuse twinning, is observed as a function of aging time and imposed strain, twinning being observed in samples containing Ni{sub 2}(Mo,Cr) precipitates. A semi-quantitative model developed on the basis of precipitate size and mode of deformation (shearing, twinning, bypassing) is able to satisfactorily account for this transition. A presentation and discussion of these results, as well as those of the mechanisms of strengthening and strain hardening, are provided.

  18. Effect of Cr and Cu addition on corrosion behavior of Ni-Ti alloys.

    PubMed

    Iijima, M; Endo, K; Ohno, H; Mizoguchi, I

    1998-03-01

    The corrosion behavior of three Ni-Ti alloys with compositions as commercial super-elastic orthodontic wires was investigated using polished plate specimens. Corrosion resistance was estimated by potentiodynamic polarization measurement in 0.9% NaCl and 1% lactic acid solutions and analysis of released metals by atomic absorption spectrophotometry. The influence of Cr and Cu addition on the structure of the surface oxide film was examined by X-ray photoelectron spectroscopy (XPS). Addition of 0.19 at% Cr had little effect on the structure of the oxide films and the corrosion resistance of the Ni-Ti alloys. For Ni-Ti-5Cu-0.3Cr alloy, the metallic Cu was enriched at the alloy/oxide film interface, resulting in increased susceptibility to pitting corrosion above +1000 mV. However, the passive current density and the amount of released Ni were not significantly increased by the addition of Cu. The study showed that small amounts of Cr and Cu added to change the super-elastic characteristics do not change the corrosion resistance of the Ni-Ti alloy freely immersed in simulated physiological environments. PMID:9663060

  19. Microstructure and Fracture Toughness of FeNiCr-TiC Composite Produced by Thermite Reaction

    NASA Astrophysics Data System (ADS)

    Xi, Wenjun; Shi, Chaoliang

    The microstructures of the FeNiCr-TiC composite produced by the rapid solidification thermite process were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The effects of aging treatment on the microstructure and fracture toughness of the composite were examined. Results showed that the FeNiCr-TiC composite was composed of ferrite (α-FeNiCr), TiC and NiAl (β phase). TiC particles in the matrix were in the shape of polygon and uniformly distributed, and their size was less than 3 µm. The β phase was coherent with the ferrite matrix, and its average size was about 50 nm. The fracture toughness of composite was 22 MPa·m1/2 without aging. When the aging temperature was below 600°C, the fracture toughness of the composite had higher plateau values and reached the maximum of 32 MPa·m1/2 at aging temperature 500°C due to the precipitation of NiAl phase on the nanometer scale. The fracture toughness decreased rapidly aged at 650°C, and then kept homology value in the range of 700 to 900°C, which was attributed to the precipitation of needle-shaped carbide (Cr/Fe)7C3 at the grain boundaries.

  20. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  1. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids were observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. The voids resulted from an excess number of oxygen vacancies near the oxidemetal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidation of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al, Cr)2O3 and Ni(Al, Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationship between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  2. Diffusion Quantum Monte Carlo predictions for bulk MnNiO3

    NASA Astrophysics Data System (ADS)

    Mitra, Chandrima; Krogel, Jaron; Reboredo, Fernando A.

    MnNiO3 is a strongly correlated transition metal oxide that has recently been investigated theoretically for its potential application as an oxygen-evolution photo-catalyst. However, there is no experimental report on critical quantities like its band gap or its bulk modulus. Recent theoretical predictions with standard functionals, such as PBE +U and HSE show large discrepancies in the band-gaps (about 1.23 eV), depending on the nature of the functional used. Hence, there is clearly a need for an accurate quantitative prediction of the band-gap in order to decide its usefulness as a photo-catalyst. In this work, we present Diffusion Quantum Monte Carlo (DMC) study of the bulk properties of MnNiO3. This includes the quasiparticle band gap for the two spin channels, the equilibrium lattice parameter and the bulk modulus. The DMC approach has already been shown to achieve excellent agreement with experimental results for other oxides such as ZnO NiO and Fe2O3. To our knowledge, MnNiO3 is the first case where this theory is applied before experiments are done. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  3. Incorporation, valence state, and electronic structure of Mn and Cr in bulk single crystal β-Ga2O3

    NASA Astrophysics Data System (ADS)

    Lovejoy, T. C.; Chen, Renyu; Yitamben, E. N.; Shutthanadan, V.; Heald, S. M.; Villora, E. G.; Shimamura, K.; Zheng, S.; Dunham, S. T.; Ohuchi, F. S.; Olmstead, M. A.

    2012-06-01

    Single crystals of transition metal (TM) doped β-Ga2O3, a wide gap semiconductor system of interest for transparent conductive oxide and diluted magnetic semiconductor applications, have been studied in the dilute, non-interacting limit (≤0.06 cation %). Based on optical absorption, particle induced x-ray emission, and Rutherford backscattering measurements, Mn does not incorporate as well as Cr, and Mn degrades the crystal quality. Using superconducting quantum interference device (SQuID) magnetometry, a Brillouin type paramagnetic magnetization is observed for Mn or Cr doped crystals with an effective number of Bohr magnetons per TM ion of 5.88 ± 0.1 or 3.95 ± 0.1, respectively. A trace ferromagnetic signal is consistent with a very small concentration of secondary phases in the Mn-doped crystal. The position of the edge in x-ray absorption near edge structure (XANES) measurements suggests that the Cr takes the 3+ valence, while a mixture of Mn2+ and Mn3+ are present; based on the absence of a prominent pre-edge feature in the XANES, both TM predominantly occupy an octahedral site in β-Ga2O3. Density functional theory (DFT) results, optical absorption and SQuID data are consistent with this assignment. While the Cr-doped crystal is conductive, the Mn-doped crystal is insulating, which is consistent with the Mn2+/Mn3+ mixed valence, assuming the Fermi level is pinned mid-gap at the Mn 2+/3+ transition level, which is predicted by DFT to be 1.8 eV above the valence band maximum.

  4. Radiation effects on interface reactions of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni)

    NASA Astrophysics Data System (ADS)

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; Rory Kennedy, J.

    2015-01-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 °C or 550 °C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reach the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick's laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.

  5. WC-Co and Cr3C2-NiCr Coatings in Low- and High-Stress Abrasive Conditions

    NASA Astrophysics Data System (ADS)

    Kašparová, Michaela; Zahálka, František; Houdková, Šárka

    2011-03-01

    The article deals with the evaluation of abrasive wear resistance and adhesive strength of thermally sprayed coatings. The main attention was paid to differences between low- and high-stress abrasive conditions of the measuring. Conclusions include the evaluation of specific properties of the WC-Co and the Cr3C2-NiCr High Velocity Oxygen Fuel coatings and the evaluation of the changes in the behavior of the abrasive media. Mainly, the relationship between the low- and high-stress abrasion conditions and the wear mechanism in the tested materials was described. For the wear test, the abrasive media of Al2O3 and SiO2 sands were chosen. During wear tests, the volume loss of the tested materials and the surface roughness of the wear tracks were measured. The wear tracks on the tested materials and abrasive sands' morphologies were observed using Scanning Electron Microscopy. It was found that high-stress abrasive conditions change the coatings' behavior very significantly, particularly that of the Cr3C2-NiCr coating. Adhesive-cohesive properties of the coatings and relationships among individual structure particles were evaluated using tensile testing. It was found that the weak bond strength among the individual splats, structure particles, and phases plays a role in the poor wear resistance of the coatings.

  6. Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

    SciTech Connect

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; Rory Kennedy, J.

    2014-10-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reach the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.

  7. Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

    DOE PAGESBeta

    Shao, Lin; Chen, Di; Wei, Chaochen; Martin, Michael S.; Wang, Xuemei; Park, Youngjoo; Dein, Ed; Coffey, Kevin R.; Sohn, Yongho; Sencer, Bulent H.; et al

    2014-10-01

    We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reachmore » the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.« less

  8. Study of certain features of the electronic structure of the ternary alloys Ni2(Mn, Fe) and Ni3(Mn, Co)

    NASA Technical Reports Server (NTRS)

    Zhukova, V. M.; Fadin, V. P.

    1981-01-01

    The changes in electronic structure related to transport processes occurring during the alloying of he alloy Ni3Mn with iron and cobalt, and the ordering of the ternary alloys thus formed are presented. The Hall effect, the absolute thermal emf, the internal saturation induction, the Nernst-Ettingshausen constant, and the electrical resistivity were measured. Results show a decrease in the contribution of hole sections of the Fermi surface to the transport process occurs together with a considerable increase in the contribution of electron sections. In this case, the mobility of 3 dimensional holes decreases and the mobility of 4s electrons increases considerably.

  9. Exploring artificial layered heterostructures of LaM'O3/LaM''O3 (M'M''= NiCr, FeCr and NiV).

    NASA Astrophysics Data System (ADS)

    Liu, J.; Kareev, M.; Freeland, J. W.; Kareev, A.; Lee, H. N.; Chakhalian, J.

    2008-03-01

    Digital synthesis of atomically sharp interfaces between strongly correlated electron systems can provide a template to build completely new materials. Here we present our results on magnetism and electronic structure in LaM'O3/LaM''O3 (M'M''= NiCr, FeCr and NiV) superlattices by using polarized X-ray spectroscopies. Using laser MBE, the (111) and (100) oriented ultra-thin superlattices were grown with alternating layer thicknesses of 1 unit cell. In the bulk, LaMO3 (M=Cr,Fe,V) are antiferromagnetic insulators while LaNiO3 is a paramagnetic metal. The evolution of element specific magnetism and charge at the interface of LFO/LCO, LNO/LVO and LNO/LCO superlattices with temperature and an applied magnetic field will be discussed in detail. The superlattice results will be contrasted to the bulk magnetic properties of the constituent layers. The work has been supported by U.S. DOD-ARO under Contract No. 0402-17291.

  10. Post-irradiation annealing behavior of neutron-irradiated FeCu, FeMnNi and FeMnNiCu model alloys investigated by means of small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Bergner, F.; Ulbricht, A.; Lindner, P.; Keiderling, U.; Malerba, L.

    2014-11-01

    Neutron irradiation of reactor pressure vessel steels gives rise to the formation of thermodynamically stable and unstable nano-features. The present work is focused on the stability of Cu-, Mn- and Ni-containing solute clusters in model alloys exposed to post-irradiation annealing. Fe0.1Cu, Fe1.2Mn0.7Ni and Fe1.2Mn0.7Ni0.1Cu (wt%) model alloys irradiated up to neutron exposures of 0.1 and 0.19 dpa (displacements per atom) were annealed at stepwise increasing temperatures in the range from 300 °C (i.e. near irradiation temperature) to 500 °C and characterized by means of small-angle neutron scattering (SANS). We have found characteristic differences in the annealing behavior of the alloys. In particular, there is a non-trivial (synergistic-antagonistic) interplay of Mn/Ni and Cu.

  11. Effects of hBN Content on the Microstructure and Properties of Atmospheric Plasma-Sprayed NiCr/Cr3C2-hBN Composite Coatings

    NASA Astrophysics Data System (ADS)

    Cao, Yuxia

    2016-04-01

    NiCr/Cr3C2-hBN composite coatings with different contents of hBN were prepared by atmospheric plasma-spray technology. The microstructural, mechanical, and tribological properties of the coatings were systematically investigated. The results show that the flowability and apparent density of NiCr/Cr3C2-hBN composite powders, as well as the microhardness and tensile strength of the NiCr/Cr3C2-hBN composite coating, gradually decrease with the increase of hBN in the composite powders. The addition of hBN is benefit to the friction coefficient of the coatings, but it is positive to the wear rate. When the content of hBN is up to 20%, the friction coefficient of the composite coating is lowest, but the wear rate of the composite coating is highest.

  12. Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

    NASA Astrophysics Data System (ADS)

    Gubbiotti, G.; Tacchi, S.; Del Bianco, L.; Bonfiglioli, E.; Giovannini, L.; Tamisari, M.; Spizzo, F.; Zivieri, R.

    2015-05-01

    Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence of the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.

  13. Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

    SciTech Connect

    Gubbiotti, G. Tacchi, S.; Del Bianco, L.; Bonfiglioli, E.; Giovannini, L.; Spizzo, F.; Zivieri, R.; Tamisari, M.

    2015-05-07

    Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence of the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.

  14. Effect of Thermal Treatments on Ni-Mn-Ga and Ni-Rich Ni-Ti-Hf/Zr High-Temperature Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Santamarta, Ruben; Evirgen, Alper; Perez-Sierra, Aquilina M.; Pons, Jaume; Cesari, Eduard; Karaman, Ibrahim; Noebe, Ron D.

    2015-11-01

    Among all the promising high-temperature shape memory alloys (HTSMAs), the Ni-Mn-Ga and the Ni-Ti-Hf/Zr systems exhibit interesting shape memory and superelastic properties that may place them in a good position for potential applications. The present work shows that thermal treatments play a crucial role in controlling the martensitic phase transformation characteristics of both systems, but in different ways. On one hand, the equilibrium phase diagram of the Ni-Mn-Ga family allows selecting compositions with high transformation temperatures and outstanding thermal stability at relatively high temperatures in air, showing no significant changes in the transformation behavior for continuous aging up to ˜5 years at 500 °C. Moreover, the excellent thermal stability correlates with a good thermal cyclic stability and an exceptional oxidation resistance of the parent phase. On the other hand, precipitation processes controlled by thermal treatments are needed to manipulate the transformation temperatures, mechanical properties, and thermal stability of Ni-rich Ni-Ti-Hf/Zr alloys to become HTSMAs. These changes in the functional properties are a consequence of the competition between the mechanical and compositional effects of the precipitates on the martensitic transformation.

  15. Analysis of the microstructure of Cr-Ni surface layers deposited on Fe{sub 3}Al by TIG

    SciTech Connect

    Ma Haijun . E-mail: hjma123@mail.sdu.edu.cn; Li Yajiang; Wang Juan

    2006-12-15

    A series of Cr-Ni alloys were overlaid on a Fe{sub 3}Al surface by tungsten inert gas arc welding (TIG) technology. The microstructure of the Cr-Ni surface layers were analysed by means of optical metallography, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that when the appropriate TIG parameters were used and Cr25-Ni13 and Cr25-Ni20 alloys were used for the overlaid materials, the Cr-Ni surface layers were crack-free. The matrix of the surface layer was austenite (A), pro-eutectoid ferrite (PF), acicular ferrite (AF), carbide-free bainite (CFB) and lath martensite (LM), distributed on the austenitic grain boundaries as well as inside the grains. The phase constituents of the Cr25-Ni13 surface layer were {gamma}-Fe, Fe{sub 3}Al, FeAl, NiAl, an Fe-C compound and an Fe-C-Cr compound. The microhardness of the fusion zone was lower than that of the Fe{sub 3}Al base metal and Cr25-Ni13 surface layer.

  16. Oxidation resistant and low coefficient of thermal expansion NiA1-CoCrAly alloy

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G. (Inventor)

    2002-01-01

    A bond coat composition for use in thermal barrier coatings comprises a NiAl--CoCrAlY matrix containing particles of AlN dispersed therein. The bond coat composition is prepared by croymilling NiAl and CoCrAlY in liquid nitrogen.

  17. Study on Optical Properties of Nanostructured NiCr Film Prepared by Magnetron Sputtering and RIE for Terahertz Applications

    NASA Astrophysics Data System (ADS)

    Gou, Jun; Wang, Jun; Li, Weizhi; Gu, Deen; Jiang, Yadong

    2015-09-01

    Nanoscale NiCr thin film has been proven to be an effective metallic terahertz (THz) absorption layer. To prepare NiCr film with a small thickness and enhanced THz absorption, a combined process of magnetron sputtering and reactive ion etching (RIE) is suggested to obtain nanostructured NiCr film with different thicknesses by precise control of process parameters and etch time. Optical characteristics tests show that both transmission and reflection of NiCr film are weakened by the RIE treatment. NiCr absorption layer is prepared in 80 × 60 infrared focal plane arrays (IRFPAs) by a combination of substrate modification process and RIE thinning process. THz absorption is effectively enhanced by RIE processes applied to the dielectric substrate and NiCr film, which generates nanoscale structures on upper and lower surfaces of NiCr absorption film for an increased specific surface area. The noise equivalent power (NEP) of the THz detection unit achieves 162.8 pW/Hz1/2, which is suitable for the application of active THz imaging. The results indicate that nanostructured NiCr film is an effective THz absorption layer for applications in thermal sensing and its absorption performance can be further improved by RIE.

  18. Growth and structure of the Ni(110)-c(2×2)Mn surface alloy: An x-ray diffraction analysis

    NASA Astrophysics Data System (ADS)

    de Santis, M.; Abad-Langlais, V.; Gauthier, Y.; Dolle, P.

    2004-03-01

    Surface x-ray diffraction was used in order to study the c(2×2) structure obtained by deposition of about 0.5 ML of Mn on Ni(110). Deposited atoms substitute Ni ones in the outermost layer, leading to a two-dimensional surface alloy with a checkerboard arrangement. The noninteger diffraction spot intensities originate mainly from a rippling of the top layer, in which the Mn atoms are shifted by 0.30±0.03 Å outwards. A weak buckling of 0.036±0.005 Å is also found in the third layer, with the Ni atoms located below the Mn site shifted outwards. This results in a surface alloy quite similar to the prototype Cu(100)-c(2×2)Mn, in which the corrugated structure was correlated to a high spin state of Mn [M. Wuttig, Y. Gauthier, and S. Blügel, Phys. Rev. Lett. 70, 3619 (1993)].

  19. Electron energy loss spectroscopy of CH/sub 3/N/sub 2/CH/sub 3/ adsorbed on Ni(100), Ni(111), Cr(100), Cr(111)

    SciTech Connect

    Schulz, M.A.

    1985-07-01

    A study of the adsorption of CH/sub 3/N/sub 2/CH/sub 3/ on Ni(100), Ni(111), Cr(100), and Cr(111) using high resolution electron energy loss spectroscopy (EELS) is presented. Under approximately the same conditions of coverage, the vibrational spectra of CH/sub 3/N/sub 2/CH/sub 3/ on these four surfaces are quite distinct from one another, implying that the CH/sub 3/N/sub 2/CH/sub 3/-substrate interaction is very sensitive to the physical and electronic structure of each surface. In addition to the room temperature studies, the evolution of surface species on the Ni(100) surface in the temperature range 300 to 425 K was studied. Analysis of the Ni(100) spectra indicates that molecular adsorption, probably through the N lone pair, occurs at room temperature. Spectra taken after annealing the CH/sub 3/N/sub 2/CH/sub 3/-Ni(100) surfaces indicate that CH and CN bond scission occurred at the elevated temperatures. Decomposition of CH/sub 3/N/sub 2/CH/sub 3/ takes place on the Ni(111), Cr(100), and Cr(111) surfaces at room temperature, as evidenced by the intensity of the carbon-metal stretch in the corresponding spectra. Possible identities of coadsorbed dissociation products are considered. The stable coverage of surface species on all four surfaces at 300 K is less than one monolayer. A general description of an electron energy loss (EEL) spectrometer is given. Followed by a more specific discussion of some recent modifications to the EEL monochromator assembly used in this laboratory. Both the previous configuration of our monochromator and the new version are briefly described, as an aid to understanding the motivation for the changes as well as the differences in operation of the two versions. For clarity, the new monochromator design is referred to as variable pass, while the previous design is referred to as double pass. A modified tuning procedure for the new monochromator is also presented. 58 refs., 11 figs.

  20. Charge transport in NdNiO3 thin films: Effects of mn-doping versus tensile strain

    NASA Astrophysics Data System (ADS)

    Chandra, Mahesh; Aziz, Fozia; Rana, Rakesh; Late, Ravikiran; Rana, D. S.; Mavani, K. R.

    2014-04-01

    We have performed a comparative study of total three films, two films of NdNiO3 deposited on SrTiO3 (STO) and NdGaO3 (NGO) single-crystals and one 10% Mn-doped thin film of NdNi0.9Mn0.1O3 deposited on NGO. We find that both, the enhanced tensile strain and the Mn-doping drive the system to an insulating state from a metallic state at high temperatures. NdNiO3/NGO film shows a metal-insulator transition, which disappears in the other two films due to opening of charge-transfer gap. These results reveal that the effect of tensile strain on the resistivity of NdNiO3 is profound at low temperatures, whereas Mn-doping clearly dominates at high temperatures.

  1. Quaternary PtMnCuX/C (X = Fe, Co, Ni, and Sn) and PtMnMoX/C (X = Fe, Co, Ni, Cu and Sn) alloys catalysts: Synthesis, characterization and activity towards ethanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Ammam, Malika; Easton, E. Bradley

    2012-10-01

    In this account, two series of quaternary PtMnCuX/C (X = Fe, Co, Ni, and Sn) and PtMnMoX/C (X = Fe, Co, Ni, Cu and Sn) alloys catalysts have been synthesized and characterized by ICP, XRD, XPS, TEM and cyclic voltammetry. XRD spectra of each series illustrated that PtMnCuX/C (X = Fe, Co and Ni) and PtMnMoX/C (X = Fe, Co, Ni and Cu) alloys have been formed without significant free Mn, Cu, Mo or X co-catalysts. For PtMnCuSn/C and PtMnMoSn/C, in addition to alloy formation, significant free Sn-oxides are present in each catalyst. Cyclic voltammetry and chronoamperometry revealed that all quaternary showed superior electrocatalytic activity towards ethanol oxidation compared to the ternary precursor. Also, shift of the onset potential of ethanol oxidation towards less positive values were also recorded with the quaternary alloys, demonstrating a facilitated oxidation with the quaternary alloys compared to ternary alloy precursor. The magnitude of the gain in potential depend on the alloy composition and PtMnMoSn/C was found to be the best of all synthetized quaternary alloys with an onset potential of ethanol oxidation of only 0.059 V vs. Ag/AgCl.

  2. Microstructure and phase evolution in laser clad chromium carbide-NiCrMoNb

    NASA Astrophysics Data System (ADS)

    Venkatesh, L.; Samajdar, I.; Tak, Manish; Doherty, Roger D.; Gundakaram, Ravi C.; Prasad, K. Satya; Joshi, S. V.

    2015-12-01

    Microstructural development in laser clad layers of Chromium carbide (CrxCy)-NiCrMoNb on SA 516 steel has been investigated. Although the starting powder contained both Cr3C2 and Cr7C3, the clad layers showed only the presence of Cr7C3. Microtexture measurements by electron back scattered diffraction (EBSD) revealed primary dendritic Cr7C3 with Ni rich FCC metallic phase being present in the interdendritic spaces. Further annealing of the laser clad layers and furnace melting of the starting powder confirmed that Cr7C3 is the primary as well as stable carbide phase in this multi component system. Increase in laser power and scanning speed progressively reduced carbide content in the laser clad layers. Increased scanning speed, which enhances the cooling rate, also led to reduction in the secondary arm spacing (λ2) of the Cr7C3 dendrites. The clad layer hardness increased with carbide content and with decreased dendrite arm spacing.

  3. Magnetic and mechanical properties of Ni-Mn-Ga/Fe-Ga ferromagnetic shape memory composite

    NASA Astrophysics Data System (ADS)

    Tan, Chang-Long; Zhang, Kun; Tian, Xiao-Hua; Cai, Wei

    2015-05-01

    A ferromagnetic shape memory composite of Ni-Mn-Ga and Fe-Ga was fabricated by using spark plasma sintering method. The magnetic and mechanical properties of the composite were investigated. Compared to the Ni-Mn-Ga alloy, the threshold field for magnetic-field-induced strain in the composite is clearly reduced owing to the assistance of internal stress generated from Fe-Ga. Meanwhile, the ductility has been significantly improved in the composite. A fracture strain of 26% and a compressive strength of 1600 MPa were achieved. Projects supported by the National Natural Science Foundation of China (Grant Nos. 51271065 and 51301054), the Program for New Century Excellent Talents in Heilongjiang Provincial Education Department, China (Grant No. 1253-NCET-009), the Youth Academic Backbone in Heilongjiang Provincial Education Department, China (Grant No. 1251G022), the Projects of Heilongjiang, China, and China Postdoctoral Science Foundation.

  4. Bioleaching of spent Zn-Mn or Ni-Cd batteries by Aspergillus species.

    PubMed

    Kim, Min-Ji; Seo, Ja-Yeon; Choi, Yong-Seok; Kim, Gyu-Hyeok

    2016-05-01

    This research explores the recovery of metals from spent Zn-Mn or Ni-Cd batteries by a bioleaching using six Aspergillus species. Two different nutrients, malt extract and sucrose, were used to produce different types of organic acids. Oxalic acid and citric acid were shown to be the dominant organic acid in malt extract and sucrose media, respectively. In the bioleaching, the metal removal was higher in sucrose media than malt extract. All species, except A. niger KUC5254, showed more than 90% removal of metals from Zn-Mn battery. For Ni-Cd battery, more than 95% of metals was extracted by A. niger KUC5254 and A. tubingensis KUC5037. As a result, A. tubingensis KUC5037 which is a non-ochratoxigenic fungus was considered to have the greatest potential for improving the safety and efficiency of the bioleaching. PMID:26584557

  5. Charge reorganization in LaMnO3 /LaNiO3 superlattice interfaces

    NASA Astrophysics Data System (ADS)

    Iori, Federico; Gloter, Alexandre; Unravel Project Team; Stem Group Team

    Functional properties of oxide heterostructurecan recently be controlled and tuned through the electronic and structural mismatch at the interface. Artificial superlattices thin film can thus present complex magnetic structure at the interface different from their corresponding bulk building blocks. In this scenario when an antiferromagnetic buk LMO and the paramagnetic bulk LNO are combined in thin filmssuperlattices, LaMnO3/LaNiO3, strong exchange bias, new metal-insulator transition or antiferromagnetic order at the interface appear. In this work we study by ab initio Density Functional Theory how the induced magnetic moments in LNO films in LMO/LMO (111)-oriented can lead to charge transfer and reorganization at the interface among the Ni and Mn metal ions for different periodicities of the superlattices (3/3, 5/5, 7/7) and how it is possible to control them through atomic intermixing at the interface.

  6. High capacitive performance of nanostructured Mn-Ni-Co oxide composites for supercapacitor

    SciTech Connect

    Luo Jianmin; Gao Bo; Zhang Xiaogang

    2008-05-06

    Nanostructured Mn-Ni-Co oxide composites (MNCO) were prepared by thermal decomposition of the precursor obtained by chemical co-precipitation of Mn, Ni and Co salts. The chemical composition and morphology were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The electrochemical capacitance of MNCO electrode was examined by cyclic voltammetry, impedance and galvanostatic charge-discharge measurements. The results showed that MNCO electrode exhibited the good electrochemical characteristics. A maximum capacitance value of 1260 F g{sup -1} could be obtained within the potential range of -0.1 to 0.4 V versus saturated calomel electrode (SCE) in 6 mol L{sup -1} KOH electrolyte.

  7. Nonlinear magnetodielectric effect in double-perovskite Gd2NiMnO6

    NASA Astrophysics Data System (ADS)

    Oh, S. H.; Choi, H. Y.; Moon, J. Y.; Kim, M. K.; Jo, Y.; Lee, N.; Choi, Y. J.

    2015-11-01

    Magnetic and dielectric properties of the double perovskite Gd2NiMnO6 were investigated. Ferromagnetic order of alternating Ni2+ and Mn4+ spins arises below {{T}\\text{C}}=134 K and an additional order of Gd3+ spins occurs at {{T}\\text{Gd}}=33 K. The formation of short-range ferromagnetic clusters accompanied by a Griffiths phase-like feature below {{T}\\text{G}}=230 K is also suggested. Under the low enough dielectric loss at low temperature regime excluding the influence of the extrinsic effect, a highly nonlinear variation of the dielectric constant was achieved in application of the magnetic fields. Our finding offers an efficient approach to accomplish intrinsically coupled functionality utilizing both magnetic and dielectric quantities.

  8. Ni-Mn based alloys as versatile catalyst for different electrochemical reactions

    NASA Astrophysics Data System (ADS)

    Aaboubi, Omar; Ali-Omar, Ahmed-Yassin; Dzoyem, Eunice; Marthe, Jimmy; Boudifa, Mohamed

    2014-12-01

    To develop large scale use of hydrogen and fuel cells as a renewable energy source it is need to increase their durability and reduce their cost mainly due to the use of precious metals. We have examined new type of the low cost binary nickel-manganese (Ni-Mn) catalysts electrodeposited from ammonium chloride bath onto copper substrates. By varying bath composition, polarization potential and essentially bath temperature the operating deposition conditions were optimized to produce Ni-Mn coatings with high active surface (e.g. spongy aspect). The outstanding catalytic activity, the durability and the versatility of the deposited films have been characterized in basic media using several electrochemical processes, such as hydrogen evolution reaction (HER), water oxidation reaction (OER) and ethanol oxidation reaction (EOR).

  9. Stacked pulse-electroplated CoNiMnP-AAO nanocomposite permanent magnets for MEMS

    NASA Astrophysics Data System (ADS)

    Wu, P. R.; Chao, T. Y.; Cheng, Y. T.

    2015-12-01

    The paper presents a CMOS compatible pulse-electroplating technique combined with a low temperature bonding process for the synthesis of CoNiMnP-AAO (anodic alumina oxide) nanocomposite films and the fabrication of stacked composite permanent magnets (PMs). The magnetic nanocomposite film exhibits the best characteristics of the coercivity of 2472 Oe, remanence of 4000 G, and {{≤ft(\\text{BH}\\right)}\\max} of 16.13 kJ m-3, in the existing CoNiMnP systems. Meanwhile, a surface magnetic flux density of 9.2 mT generated by a 15-layer-stacked composite PM with a volume of 9 mm3 has shown the potential for various magnetic microelectromechanical systems (MEMS) fabrication using the nanocomposite material.

  10. Optimization of the magnetocaloric effect in Ni-Mn-In alloys: A theoretical study

    SciTech Connect

    Sokolovskiy, V. V.; Buchelnikov, V. D.; Entel, P.

    2012-10-15

    Based on ab initio and Monte Carlo simulations, we study the influence of the strength of the magnetic exchange parameters on the inverse and conventional magnetocaloric effect in the Ni{sub 50}Mn{sub 34}In{sub 16} Heusler alloy using the mixed Potts and Blume-Emery-Griffiths model Hamiltonian. Within the proposed model, the temperature dependences of the magnetization, tetragonal deformation, and adiabatic temperature changes for magnetic field variation are obtained. It is first shown that a decrease in the magnetic exchange interactions leads to increased values of the magnetocaloric effect. We suppose that a reduction of the exchange interactions in the Ni-Mn-In alloy can be realized by the doping with nonmagnetic atoms such as B, Si, Zn, Cu, etc.

  11. on the High-Temperature Performance of Ni-Based Welding Material NiCrFe-7

    NASA Astrophysics Data System (ADS)

    Mo, Wenlin; Lu, Shanping; Li, Dianzhong; Li, Yiyi

    2014-10-01

    The effects of M 23C6 ( M = Cr, Fe) on the high-temperature performance of the NiCrFe-7 welding rods and weld metals were studied by high-temperature tensile tests and microstructure analysis. M 23C6 at the grain boundaries (GBs) has a cube-on-cube coherence with one grain in the NiCrFe-7 weld metals, and the adjacent M 23C6 has the coherence relationship with the same grain. The grain with a coherent M 23C6 has a Cr-depletion region. The number and size of M 23C6 particles can be adjusted by heat treatment and alloying. There are two temperatures [ T E1: 923 K to 1083 K (650 °C to 810 °C) and T E2: 1143 K to 1203 K (870 °C to 930 °C)] at which the GBs and grains of the NiCrFe-7 welding rod have equal strength during the high-temperature tensile test. When the temperatures are between T E1 and T E2, the strength of the GBs is lower than that of the grains, and the tensile fractures are intergranular. When the temperatures are below T E1 or over T E2, the strength of the GBs is higher than that of the grains, and the tensile fractures are dimples. M 23C6 precipitates at the GBs, which deteriorates the ductility of the welding rods at temperature between T E1 and T E2. M 23C6 aggravates ductility-dip-cracking (DDC) in the weld metals. The addition of Nb and Ti can form MX ( M = Ti, Nb, X = C, N), fix C in grain, decrease the initial precipitation temperature of M 23C6, and mitigate the precipitation of M 23C6, which is helpful for minimizing DDC in the weld.

  12. Immiscibility in the NiFe2O4-NiCr2O4 Spinel Binary

    SciTech Connect

    S Ziemniak

    2004-08-13

    The solid solution behavior of the Ni(Fe{sub 1-n}Cr{sub n}){sub 2}O{sub 4} spinel binary is investigated in the temperature range 400-1200 C. Non-ideal solution behavior, as exhibited by non-linear changes in lattice parameter with changes in n, is observed in a series of single-phase solids air-cooled from 1200 C. Air-annealing for one year at 600 C resulted in partial phase separation in a spinel binary having n = 0.5. Spinel crystals grown from NiO, Fe{sub 2}O{sub 3} and Cr{sub 2}O{sub 3} reactants, mixed to give NiCrFeO{sub 4}, by Ostwald ripening in a molten salt solvent, exhibited single phase stability down to about 750 C (the estimated consolute solution temperature, T{sub cs}). A solvus exists below T{sub cs}. The solvus becomes increasingly asymmetric at lower temperatures and extrapolates to n values of 0.2 and 0.7 at 300 C. The extrapolated solvus is shown to be consistent with that predicted using a primitive regular solution model in which free energies of mixing are determined entirely from changes in configurational entropy at room temperature.

  13. Nickel permanganate as a precursor in the synthesis of a NiMn{sub 2}O{sub 4} spinel

    SciTech Connect

    Schmidt, Jorge A.; Sagua, Aurora E. . E-mail: arsagua@criba.edu.ar; Bazan, Julio C.; Prat, Maria R.; Braganza, Maria E.; Moran, Emilio . E-mail: emoran@quim.ucm.es

    2005-04-20

    The present study describes the preparation, characterization, and thermal decomposition of the compound Ni(MnO{sub 4}){sub 2}.xH{sub 2}O, which was synthesized by a coprecipitation method at a low temperature. The role of this compound as a precursor in the synthesis of a Ni-Mn spinel was determined via X-ray, TG-DTA, electron diffraction, and EDAX measurements.

  14. Evaluation of Ceria-Added Cr3C2-25(NiCr) Coating on Three Superalloys under Simulated Incinerator Environment

    NASA Astrophysics Data System (ADS)

    Mudgal, Deepa; Singh, Surendra; Prakash, Satya

    2015-02-01

    Cr3C2-25(NiCr) coating is widely used in wear, erosion and corrosion applications. In the present study, D-gun-sprayed Cr3C2-25(NiCr) coatings with and without 0.4 wt.% ceria incorporated were deposited on Superni 718, Superni 600 and Superco 605 substrates. Hot-corrosion runs were conducted in 40 %Na2SO4-40 %K2SO4-10 %NaCl-10 %KCl environment at 900 °C for 100 cycles. Corrosion kinetics was monitored using weight gain measurements. Characterization of corrosion products was carried out by field-emission scanning electron microscopy (FESEM)/energy-dispersive spectroscopy (EDS) and x-ray diffraction (XRD) techniques. It was observed that Cr3C2-25(NiCr) coating with and without added ceria deposited on both of the Ni-based alloys showed resistance to corrosion under the given environment. Addition of ceria enhanced the adherence of the oxide to the coating during the corrosion run and reduced the overall weight gain. However, Cr3C2-25(NiCr)-coated Superco 605 did not perform satisfactorily under this environment.

  15. Weak-beam imaging of dissociated dislocations in HVEM-irradiated Fe-Ni-Cr alloys

    SciTech Connect

    King, S.L.; Jenkins, M.L.; Kirk, M.A.; English, C.A.

    1992-06-01

    We report here on studies by weak-beam electron microscopy of the evolution of microstructures at and near preexisting line dislocations in a number of Fe-Ni-Cr alloys under electronirradiation in a high-voltage electron microscope (HVEM). The detailed observations are discussed in terms of dislocation climb mechanisms in these materials and a model based on interstitial pipe diffusion.

  16. Characterization of Ni-Cr alloys using different casting techniques and molds.

    PubMed

    Chen, Wen-Cheng; Teng, Fu-Yuan; Hung, Chun-Cheng

    2014-02-01

    This study differentiated the mechanical properties of nickel-chromium (Ni-Cr) alloys under various casting techniques (different casting molds and casting atmospheres). These techniques were sampled by a sand mold using a centrifugal machine in ambient air (group I) and electromagnetic induction in an automatic argon castimatic casting machine (group II). The specimen casting used a graphite mold by a castimatic casting machine (group III). The characteristics of the Ni-Cr alloys, yield and ultimate tensile strength, bending modulus, microhardness, diffraction phase, grindability, ability to spring back, as well as ground microstructure and pattern under different casting conditions were evaluated. The group III specimens exhibited the highest values in terms of strength, modulus, hardness, and grindability at a grind rate of 500 rpm. Moreover, group III alloys exhibited smaller grain sizes, higher ability to spring back, and greater ductility than those casted by sand investment (groups I and II). The main factor, "casting mold," significantly influenced all mechanical properties. The graphite mold casting of the Ni-Cr dental alloys in a controlled atmosphere argon casting system provided an excellent combination of high mechanical properties and good ability to spring back, and preserved the ductile properties for application in Ni-Cr porcelain-fused system. The results can offer recommendations to assist a prosthetic technician in selecting the appropriate casting techniques to obtain the desired alloy properties. PMID:24411373

  17. Solute transport during the cyclic oxidation of Ni-Cr-Al alloys. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.

    1982-01-01

    Important requirements for protective coatings of Ni-Cr-Al alloys for gas turbine superalloys are resistance to oxidation accompanied by thermal cycling, resistance to thermal fatigue cracking. The resistance to oxidation accompanied by thermal cycling is discussed. The resistance to thermal fatigue cracking is also considered.

  18. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    DOE PAGESBeta

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; Gao, Michael C.; Tang, Zhi; Poplawsky, Jonathan D.; Liaw, Peter K.

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

  19. [Ultra-structural study of Ni-Cr alloys used in joint prosthesis].

    PubMed

    Bennani, A; Amine, M; Ezzahi, A; Chafii, A; Eladioui, S

    2014-12-01

    Ni-Cr alloys used in denture set, which have excellent mechanical properties, have a chemical and electrochemical inertia that depends on their composition and their microstructure. The objective of our work was to study the ultrastructure of the Ni-Cr alloy exposed to a free corrosion and a chemical analysis of surface depending on its composition. For this, five electrodes Ni-Cr alloy were prepared at the prosthesis laboratory by varying their composition. An analysis of the ultrastructure of the samples made by Scanning Electron Microscopy (SEM) samples was performed as well as a chemical analysis of their spectra. Prior to any manipulation, analysis by SEM of electrode number 5 (100% new metal) shows an altered surface. The electrode 3 (75% new metal) also presents an uneven surface. After a week in a free corrosion in Meyer solution at pH = 6.5, the electrode 5 shows a widespread intergranular and pitting corrosion. The same electrode 3 (75% new metal) after one week immersion in Ringer's solution at pH 7.9, shows a widespread intergranular and pitting corrosion. After electrochemical testing in Ringer's solution at pH 5, the SEM for electrode 1 (100% recovered metal) shows a very rugged structure with an important crevice corrosion. The composition and terms of shaping the Ni-Cr alloy influence its microstructure and at the same time its electrochemical behavior. PMID:25980097

  20. Investigation of heat-resistant layered coating of Al-Cr-Ni

    NASA Astrophysics Data System (ADS)

    Shmorgun, V. G.; Trykov, Y. P.; Bogdanov, A. I.; Taube, A. O.

    2016-02-01

    The paper shows the transformation of the structure and phase composition of the layered coating system Al-Cr-Ni, obtained by the heat treatment of multilayered composite H20N80+AD1, welded by explosion, in the time range 1-300 hours. The cyclic heat resistance of the coating at 1150 ° C is studied.

  1. Microstructure and Properties of HVOF-Sprayed Ni-50Cr Coatings

    SciTech Connect

    Joel A. Simpson; Terry C. Totemeier; Richard N. Wright

    2006-06-01

    Thermal spray coatings represent a potential cost-effective means of protecting structural components in advanced fossil energy systems. Previous work at the INL has focused on relationships between thermal spray processing conditions, structure, and properties in alumina- and silica-forming coatings, namely Fe3Al, FeAl, and Mo-Si-B alloys. This paper describes the preparation and characterization of chromia-forming Ni-50%Cr coatings, an alloy similar to the INCOCLAD 671 cladding, which has shown excellent performance in the Niles Plant service tests. The structure and properties of Ni-50Cr coatings are similar to other HVOF-sprayed metallic coatings: a typical lamellar microstructure is observed with essentially no porosity and little oxide. The microhardness and compressive residual stress both increase with increased spray particle velocity. Corrosion tests were performed on a variety of free-standing coatings (removed from the substrate, wrought Fe3Al alloy, and Grade 91 steel in a simulated coal combustion gas (N2-10%CO-5%CO2-2%H2O-0.12%H2S) and gas-slag environments (same gas, with iron sulfide powder in contact with the coating surface). The coatings tested included Fe3Al, FeAl, and Ni-50Cr alloys sprayed at different velocities. In these tests the iron aluminides in wrought and coating form showed the best performance, with Ni-50Cr coatings slightly worse; the Grade 91 steel was severely attacked.

  2. Chemical compatibility of uranium carbides with Cr-Fe-Ni alloys

    SciTech Connect

    Beahm, E.C.; Culpepper, C.A.

    1981-08-01

    This paper discusses the chemical compatibility of uranium carbides and Cr-Fe-Ni alloys, which has been evaluated by thermodynamic modeling and experimental phase studies. Two reaction temperatures, 973 and 1273 K, were used to simulate normal and overtemperature operation of advanced liquid-metal fast breeder reactor fuel-cladding couples. 27 refs.

  3. Evolution of oxide scale on a Ni-Mo-Cr alloy at 900 deg. C

    SciTech Connect

    Ul-Hamid, A. . E-mail: anwar@kfupm.edu.sa; Mohammed, A.I.; Al-Jaroudi, S.S.; Tawancy, H.M.; Abbas, N.M.

    2007-01-15

    The cyclic oxidation behavior of a Ni-Mo-Cr alloy was studied in air at 900 deg. C for exposure periods of up to 1000 h. The morphology, microstructure and composition of the oxide scale was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Oxidation kinetics was determined by weight gain measurements. The results show that steady state oxidation was achieved within 1 h of exposure. During transient oxidation, the alloy grain boundaries intersecting the alloy surface became depleted in Ni and enriched in Mo and Cr. The scale initially formed at the surface was NiO which grew outwardly. However, a protective Cr{sub 2}O{sub 3} layer developed, rapidly retarding the rate of oxidation. Formation of NiMoO{sub 4} was also observed. The presence of Mo in the alloy facilitated the formation of a Cr{sub 2}O{sub 3} layer at an early stage of oxidation. The alloy exhibited considerable oxide spalling during prolonged exposure.

  4. Structural transition of spinel compound NiCr2O4 at ferrimagnetic transition temperature

    NASA Astrophysics Data System (ADS)

    Ishibashi, H.; Yasumi, T.

    Magnetic properties and crystal structure of spinel compound NiCr2O4 have been investigated by magnetization and high-resolution X-ray powder diffraction measurements. The structural transition from tetragonal to orthorhombic symmetry was observed at ferrimagnetic transition temperature. This crystal distortion is related to the magnetic ordering of ferrimagnetic component.

  5. Systematics of Ni, Co, Cr and V in Olivine from Planetary Melt Systems: Martian Basalts

    NASA Technical Reports Server (NTRS)

    Herd, C. D. K.; Jones, J. H.; Shearer, C. K.; Papike, J. J.

    2001-01-01

    Secondary Ion Mass Spectrometry (SIMS) data for Ni, Co, Cr, and V in olivine in martian basalts is compared to data from lunar and terrestrial basalts. We use experimentally-derived and published D values to calculate as-yet unsampled, olivine-bearing, non-cumulus melt compositions. Additional information is contained in the original extended abstract.

  6. Effect of Mn Addition on dc-Electrical Degradation of Multilayer Ceramic Capacitor with Ni Internal Electrode

    NASA Astrophysics Data System (ADS)

    Morita, Koichiro; Mizuno, Youichi; Chazono, Hirokazu; Kishi, Hiroshi

    2002-11-01

    The effect of Mn addition on the microstructure and electrical properties, especially on the dc-electrical degradation, of the X7R-type multilayer ceramic capacitor with Ni internal electrode (Ni-MLCC) with thin active layers was investigated. As the amount of Mn increased, grain growth was suppressed, and the temperature characteristic (TC) curve was flattened. I-V characteristic measurements revealed that nonlinearity coefficient (α) at a high electric field of more than 10 V/μm was decreased, and the lifetime during the highly accelerated lifetime testing (HALT) under 20 V/μm was improved, as the Mn content increased. It was found that Mn addition caused the change of the electrical properties of the grain boundary (GB). The effect of Mn on dc-electrical degradation during HALT was investigated by introducing impedance measurement at elevated temperatures from the microstructural view point. The roles of Mn on dc-electrical degradation during HALT were proposed.

  7. Growth of NiCo2O4@MnMoO4 Nanocolumn Arrays with Superior Pseudocapacitor Properties.

    PubMed

    Cui, Chunyu; Xu, Jiantie; Wang, Lei; Guo, Di; Mao, Minglei; Ma, Jianmin; Wang, Taihong

    2016-04-01

    Three-dimensional heterostructured NiCo2O4@MnMoO4 nanocolumn arrays (NCAs) on Ni foam were first fabricated through an improved two-step hydrothermal process associated with a successive annealing treatment. The hybrid NiCo2O4@MnMoO4 electrode exhibited remarkable pseudocapacitor property with high initial mass specific capacitance of 1705.3 F g(-1) at 5 mA cm(-2), and retained 92.6% after 5000 cycles, compared to the bare NiCo2O4 electrode with 839.1 F g(-1) and 90.9%. The excellent capacitive property of the NiCo2O4@MnMoO4 hydrid was attributed to its high-electron/ion-transfer rate, large electrolyte infiltrate area, and more electroactive reaction sites. PMID:26978426

  8. Magnetostructural phase transition in off-stoichiometric Ni-Mn-In Heusler alloy ribbons with low In content

    NASA Astrophysics Data System (ADS)

    González-Legarreta, L.; González-Alonso, D.; Rosa, W. O.; Caballero-Flores, R.; Suñol, J. J.; González, J.; Hernando, B.

    2015-06-01

    We report features of microstructure, martensitic transformation, magnetic properties and magnetocaloric effect in three off-stoichiometric Ni45Mn44In11, Ni47Mn41In12and Ni48Mn39In13 (nominal-compositions) alloys ribbons. They were selected in the 7.8Ni content in the decrease of magnetization observed in two alloys with respect to the third one with the lowest e/a. Ni content effect on the antiferromagnetic interaction present in the martensitic phase of the alloys ribbons is also evidenced.

  9. Adsorption and diffusion of fluorine on Cr-doped Ni(111) surface: Fluorine-induced initial corrosion of non-passivated Ni-based alloy

    NASA Astrophysics Data System (ADS)

    Ren, Cui-Lan; Han, Han; Gong, Wen-Bin; Wang, Cheng-Bin; Zhang, Wei; Cheng, Cheng; Huai, Ping; Zhu, Zhi-Yuan

    2016-09-01

    Adsorption and diffusion behaviors of fluorine on Cr-doped Ni(111) surface are investigated by using first-principles simulation. It shows that the Cr in the Cr-doped Ni(111) surface serve a trap site for fluorine with adsorption energy 3.52 eV, which is 1.04 eV higher than that on Ni(111) surface. Moreover, the Cr atom is pulled out the surface for 0.41 Å after the fluorine adsorption, much higher than that on Ni(111) surface. Further diffusion behaviors analysis confirms the conclusion because the fluorine diffusion from neighbored sites onto the Cr top site is an energy barrierless process. Detailed electronic structure analysis shows that a deeper hybrid state of F 2 p-Cr 3 d indicates a strong Fsbnd Cr interaction. The Nisbnd Cr bond is elongated and weakened due to the new formed Fsbnd Cr bonding. Our results help to understanding the basic fluorine-induced initial corrosion mechanism for Ni-based alloy in molten salt environment.

  10. Deformation and fracture of a directionally solidified NiAl-28Cr-6Mo eutectic alloy

    NASA Technical Reports Server (NTRS)

    Chen, X. F.; Johnson, D. R.; Noebe, R. D.; Oliver, B. F.

    1995-01-01

    A directionally solidified alloy based on the NiAl-(Cr, Mo) eutectic was examined by transmission and scanning electron microscopy to characterize the microstructure and room temperature deformation and fracture behavior. The microstructure consisted of a lamellar morphology with a group of zone axes (111) growth direction for both the NiAl and (Cr, Mo) phases. The interphase boundary between the eutectic phases was semicoherent and composed of a well-defined dislocation network. In addition, a fine array of coherent NiAl precipitates was dispersed throughout the (Cr, Mo) phase. The eutectic morphology was stable at 1300 K with only coarsening of the NiAl precipitates occurring after heat treatment for 1.8 ks (500 h). Fracture of the aligned eutectic is characterized primarily by a crack bridging/renucleation mechanism and is controlled by the strength of the semicoherent interface between the two phases. However, contributions to the toughness of the eutectic may arise from plastic deformation of the NiAl phase and the geometry associated with the fracture surface.

  11. Influence of Ni-Cr substitution on the magnetic and electric properties of magnesium ferrite nanomaterials

    SciTech Connect

    Iqbal, Muhammad Javed; Ahmad, Zahoor; Meydan, Turgut; Nlebedim, Ikenna Cajetan

    2012-02-15

    Graphical abstract: Variation of saturation magnetization (M{sub S}) and magnetocrystalline anisotropy coefficient (K{sub 1}) with Ni-Cr content for Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0-0.5). Highlights: Black-Right-Pointing-Pointer Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} are synthesized by novel PEG assisted microemulsion method. Black-Right-Pointing-Pointer High field regime of M-H loops are modeled using Law of Approach to saturation. Black-Right-Pointing-Pointer A considerable increase in the value of M{sub S} from 148 kA/m to 206 kA/m is achieved Black-Right-Pointing-Pointer {rho}{sup RT} enhanced to the order of 10{sup 9} {Omega}cm at potential operational range around 300 K. -- Abstract: The effect of variation of composition on the structural, morphological, magnetic and electric properties of Mg{sub 1-x}Ni{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x = 0.0-0.5) nanocrystallites is presented. The samples were prepared by novel polyethylene glycol (PEG) assisted microemulsion method with average crystallite size of 15-47 nm. The microstructure, chemical, and phase analyses of the samples were studied by the scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray fluorescence (ED-XRF), and X-ray diffraction (XRD). Compositional variation greatly affected the magnetic and structural properties. The high-field regimes of the magnetic loops are modelled using the Law of Approach (LOA) to saturation in order to extract information about their anisotropy and the saturation magnetization. Thermal demagnetization measurements are carried out using VSM and significant enhancement of the Curie temperature from 681 K to 832 K has been achieved by substitution of different contents of Ni-Cr. The dc-electrical resistivity ({rho}{sup RT}) at potential operational range around 300 K is increased from 7.5 Multiplication-Sign 10{sup 8} to 4.85 Multiplication-Sign 10{sup 9} {Omega}cm with the increase in Ni-Cr contents

  12. Intermartensitic Transformation and Enhanced Exchange Bias in Pd (Pt) -doped Ni-Mn-Sn alloys.

    PubMed

    Dong, S Y; Chen, J Y; Han, Z D; Fang, Y; Zhang, L; Zhang, C L; Qian, B; Jiang, X F

    2016-01-01

    In this work, we studied the phase transitions and exchange bias of Ni50-xMn36Sn14Tx (T = Pd, Pt; x = 0, 1, 2, 3) alloys. An intermartensitic transition (IMT), not observed in Ni50Mn36Sn14 alloy, was induced by the proper application of negative chemical pressure by Pd(Pt) doping in Ni50-xMn36Sn14Tx (T = Pd, Pt) alloys. IMT weakened and was suppressed with the increase of applied field; it also disappeared with further increase of Pd(Pt) content (x = 3 for Pd and x = 2 for Pt). Another striking result is that exchange bias effect, ascribed to the percolating ferromagnetic domains coexisting with spin glass phase, is notably enhanced by nonmagnetic Pd(Pt) addition. The increase of unidirectional anisotropy by the addition of Pd(Pt) impurities with strong spin-orbit coupling was explained by Dzyaloshinsky-Moriya interactions in spin glass phase. PMID:27170057

  13. Magneto Caloric Effect in Ni-Mn-Ga alloys: First Principles and Experimental studies

    NASA Astrophysics Data System (ADS)

    Odbadrakh, Khorgolkhuu; Nicholson, Don; Brown, Gregory; Rusanu, Aurelian; Rios, Orlando; Hodges, Jason; Safa-Sefat, Athena; Ludtka, Gerard; Eisenbach, Markus; Evans, Boyd

    2012-02-01

    Understanding the Magneto-Caloric Effect (MCE) in alloys with real technological potential is important to the development of viable MCE based products. We report results of computational and experimental investigation of a candidate MCE materials Ni-Mn-Ga alloys. The Wang-Landau statistical method is used in tandem with Locally Self-consistent Multiple Scattering (LSMS) method to explore magnetic states of the system. A classical Heisenberg Hamiltonian is parametrized based on these states and used in obtaining the density of magnetic states. The Currie temperature, isothermal entropy change, and adiabatic temperature change are then calculated from the density of states. Experiments to observe the structural and magnetic phase transformations were performed at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on alloys of Ni-Mn-Ga and Fe-Ni-Mn-Ga-Cu. Data from the observations are discussed in comparison with the computational studies. This work was sponsored by the Laboratory Directed Research and Development Program (ORNL), by the Mathematical, Information, and Computational Sciences Division; Office of Advanced Scientific Computing Research (US DOE), and by the Materials Sciences and Engineering Division; Office of Basic Energy Sciences (US DOE).

  14. Influence of volume magnetostriction on the thermodynamic properties of Ni-Mn-Ga shape memory alloys

    SciTech Connect

    Kosogor, Anna; L'vov, Victor A.; Cesari, Eduard

    2015-10-07

    In the present article, the thermodynamic properties of Ni-Mn-Ga ferromagnetic shape memory alloys exhibiting the martensitic transformations (MTs) above and below Curie temperature are compared. It is shown that when MT goes below Curie temperature, the elastic and thermal properties of alloy noticeably depend on magnetization value due to spontaneous volume magnetostriction. However, the separation of magnetic parts from the basic characteristics of MT is a difficult task, because the volume magnetostriction does not qualitatively change the transformational behaviour of alloy. This problem is solved for several Ni-Mn-Ga alloys by means of the quantitative theoretical analysis of experimental data obtained in the course of stress-strain tests. For each alloy, the entropy change and the transformation heat evolved in the course of MT are evaluated, first, from the results of stress-strain tests and, second, from differential scanning calorimetry data. For all alloys, a quantitative agreement between the values obtained in two different ways is observed. It is shown that the magnetic part of transformation heat exceeds the non-magnetic one for the Ni-Mn-Ga alloys undergoing MTs in ferromagnetic state, while the elevated values of transformation heat measured for the alloys undergoing MTs in paramagnetic state are caused by large MT strains.

  15. Strain behavior and lattice dynamics in Ni50Mn35In15

    NASA Astrophysics Data System (ADS)

    Salazar Mejía, C.; Nayak, A. K.; Schiemer, J. A.; Felser, C.; Nicklas, M.; Carpenter, M. A.

    2015-10-01

    The lattice dynamics in the polycrystalline shape-memory Heusler alloy Ni50Mn35In15 have been studied by means of resonant ultrasound spectroscopy (RUS). RUS spectra were collected in a frequency range 100-1200 kHz between 10 and 350 K. Ni50Mn35In15 exhibits a ferromagnetic transition at 313 K in the austenite phase and a martensitic transition at 248 K accompanied by a change of the magnetic state. Furthermore it displays a paramagnetic to ferrimagnetic transition within the martensitic phase. We determined the temperature dependence of the shear modulus and the acoustic attenuation of Ni50Mn35In15 and compared it with magnetization data. Following the structural softening, which accompanies the martensitic transition as a pretransitional phenomenon, a strong stiffening of the lattice is observed at the martensitic magneto-structural transition. Only a weak magnetoelastic coupling is evidenced at the Curie temperatures both in austenite and martensite phases. The large acoustic damping in the martensitic phase compared with the austenitic phase reflects the motion of the twin walls, which freezes out in the low temperature region.

  16. Strain behavior and lattice dynamics in Ni50Mn35In15.

    PubMed

    Salazar Mejía, C; Nayak, A K; Schiemer, J A; Felser, C; Nicklas, M; Carpenter, M A

    2015-10-21

    The lattice dynamics in the polycrystalline shape-memory Heusler alloy Ni50Mn35In15 have been studied by means of resonant ultrasound spectroscopy (RUS). RUS spectra were collected in a frequency range 100-1200 kHz between 10 and 350 K. Ni50Mn35In15 exhibits a ferromagnetic transition at 313 K in the austenite phase and a martensitic transition at 248 K accompanied by a change of the magnetic state. Furthermore it displays a paramagnetic to ferrimagnetic transition within the martensitic phase. We determined the temperature dependence of the shear modulus and the acoustic attenuation of Ni50Mn35In15 and compared it with magnetization data. Following the structural softening, which accompanies the martensitic transition as a pretransitional phenomenon, a strong stiffening of the lattice is observed at the martensitic magneto-structural transition. Only a weak magnetoelastic coupling is evidenced at the Curie temperatures both in austenite and martensite phases. The large acoustic damping in the martensitic phase compared with the austenitic phase reflects the motion of the twin walls, which freezes out in the low temperature region. PMID:26418569

  17. Influence of growth conditions on exchange bias of NiMn-based spin valves

    SciTech Connect

    Wienecke, Anja; Kruppe, Rahel; Rissing, Lutz

    2015-05-07

    As shown in previous investigations, a correlation between a NiMn-based spin valve's thermal stability and its inherent exchange bias exists, even if the blocking temperature of the antiferromagnet is clearly above the heating temperature and the reason for thermal degradation is mainly diffusion and not the loss of exchange bias. Samples with high exchange bias are thermally more stable than samples with low exchange bias. Those structures promoting a high exchange bias are seemingly the same suppressing thermally induced diffusion processes (A. Wienecke and L. Rissing, “Relationship between thermal stability and layer-stack/structure of NiMn-based GMR systems,” in IEEE Transaction on Magnetic Conference (EMSA 2014)). Many investigations were carried out on the influence of the sputtering parameters as well as the layer thickness on the magnetoresistive effect. The influence of these parameters on the exchange bias and the sample's thermal stability, respectively, was hardly taken into account. The investigation described here concentrates on the last named issue. The focus lies on the influence of the sputtering parameters and layer thickness of the “starting layers” in the stack and the layers forming the (synthetic) antiferromagnet. This paper includes a guideline for the evaluated sputtering conditions and layer thicknesses to realize a high exchange bias and presumably good thermal stability for NiMn-based spin valves with a synthetic antiferromagnet.

  18. Kinetics of discontinuous precipitation in Cu-20Ni-20Mn alloy

    NASA Astrophysics Data System (ADS)

    Xie, Wei-bin; Wang, Qiang-song; Xie, Guo-liang; Mi, Xu-jun; Liu, Dong-mei; Gao, Xue-Cheng

    2016-03-01

    The morphology and growth kinetics of discontinuous precipitation (DP) in a Cu-20Ni-20Mn alloy were investigated in the temperature range of 523-673 K by optical microscopy, scanning electron microscopy, and transmission electron microscopy. A lamellar mixed structure consisting of alternating lamellae of a matrix and NiMn phase was observed in DP colonies. The volume fraction of regions formed by a DP reaction was determined by quantitative metallographic measurements. The kinetics of DP was evaluated on the basis of the Johnson-Mehl-Avrami-Kolmogorov equation, which resulted in a time exponent of approximately 1.5. We confirmed that the nucleation of the discontinuous precipitate was confined to grain edges or boundaries at an early stage of the reaction. The activation energy of DP process was determined to be approximately (72.7 ± 7.2) kJ/mol based on the Arrhenius equation; this result suggests that DP is controlled by grain boundary diffusion. The hardness values exhibited good correlation with the volume fraction of DP; this correlation was attributed to the presence of the ordered NiMn phase.

  19. Intermartensitic Transformation and Enhanced Exchange Bias in Pd (Pt) -doped Ni-Mn-Sn alloys

    PubMed Central

    Dong, S. Y.; Chen, J. Y.; Han, Z. D.; Fang, Y.; Zhang, L.; Zhang, C. L.; Qian, B.; Jiang, X. F.

    2016-01-01

    In this work, we studied the phase transitions and exchange bias of Ni50−xMn36Sn14Tx (T = Pd, Pt; x = 0, 1, 2, 3) alloys. An intermartensitic transition (IMT), not observed in Ni50Mn36Sn14 alloy, was induced by the proper application of negative chemical pressure by Pd(Pt) doping in Ni50−xMn36Sn14Tx (T = Pd, Pt) alloys. IMT weakened and was suppressed with the increase of applied field; it also disappeared with further increase of Pd(Pt) content (x = 3 for Pd and x = 2 for Pt). Another striking result is that exchange bias effect, ascribed to the percolating ferromagnetic domains coexisting with spin glass phase, is notably enhanced by nonmagnetic Pd(Pt) addition. The increase of unidirectional anisotropy by the addition of Pd(Pt) impurities with strong spin-orbit coupling was explained by Dzyaloshinsky-Moriya interactions in spin glass phase. PMID:27170057

  20. Half-metallic Ni2MnSn Heusler alloy prepared by rapid quenching

    NASA Astrophysics Data System (ADS)

    Nazmunnahar, M.; Ryba, T.; del Val, J. J.; Ipatov, M.; González, J.; Hašková, V.; Szabó, P.; Samuely, P.; Kravcak, J.; Vargova, Z.; Varga, R.

    2015-07-01

    We have employed melt-spinning method to produce Ni2MnSn-based half-metallic Heusler alloy. It allows fast and simple production of large amount of materials in a single production step avoiding high temperature post-production annealing. Microstructural, magnetic and spin polarization study of Ni2MnSn ribbon is used for characterization. SEM analysis reveals the polycrystalline structure with the columnar crystals grown perpendicularly to the ribbon plane. A single-phase austenite with L21 structure was confirmed by X-ray. Magnetic measurements shows the ordinary ferromagnetic behavior with Curie temperature 344 K and magnetic moment 4.08 μB/f.u. Particular crystal structure leads to the well defined anisotropy having an easy plane in the ribbon's plane. Finally, the spin polarization parameter P0 estimated by Point-Contact Andreev-reflection Spectroscopy is varying in the range 40-70% for Ni2MnSn which is comparable with other values reported earlier for other Heusler alloys.

  1. Preparation and characterization of nanostructured NiO/MnO{sub 2} composite electrode for electrochemical supercapacitors

    SciTech Connect

    Liu Enhui Li Wen; Li Jian; Meng Xiangyun; Ding Rui; Tan Songting

    2009-05-06

    Nanostructured nickel-manganese oxides composite was prepared by the sol-gel and the chemistry deposition combination new route. The surface morphology and structure of the composite were characterized by scanning electron microscope and X-ray diffraction. The as-synthesized NiO/MnO{sub 2} samples exhibit higher surface area of 130-190 m{sup 2} g{sup -1}. Cyclic voltammetry and galvanostatic charge/discharge measurements were applied to investigate the electrochemical performance of the composite electrodes with different ratios of NiO/MnO{sub 2}. When the mass ratio of MnO{sub 2} and NiO in composite material is 80:20, the specific capacitance value of NiO/MnO{sub 2} calculated from the cyclic voltammetry curves is 453 F g{sup -1}, for pure NiO and MnO{sub 2} are 209, 330 F g{sup -1} in 6 mol L{sup -1} KOH electrolyte and at scan rate of 10 mV s{sup -1}, respectively. The specific capacitance of NiO/MnO{sub 2} electrode is much larger than that of each pristine component. Moreover, the composite electrodes showed high power density and stable electrochemical properties.

  2. Magnetic properties and hyperfine interactions in Cr8, Cr7Cd, and Cr7Ni molecular rings from 19F-NMR

    SciTech Connect

    Bordonali, L; Garlatti, E; Casadei, C M; Furukawa, Y; Lascialfari, A; Carretta, S; Troiani, F; Timco, G; Winpenny, R E; Borsa, F

    2014-04-14

    A detailed experimental investigation of the 19F nuclear magnetic resonance is made on single crystals of the homometallic Cr₈ antiferromagnetic molecular ring and heterometallic Cr₇Cd and Cr₇ Ni rings in the low temperature ground state. Since the F- ion is located midway between neighboring magnetic metal ions in the ring, the 19F-NMR spectra yield information about the local electronic spin density and ¹⁹F hyperfine interactions. In Cr8, where the ground state is a singlet with total spin S T = 0, the ¹⁹F-NMR spectra at 1.7 K and low external magnetic field display a single narrow line, while when the magnetic field is increased towards the first level crossing field, satellite lines appear in the ¹⁹F-NMR spectrum, indicating a progressive increase in the Boltzmann population of the first excited state S T = 1. In the heterometallic rings, Cr₇Cd and Cr₇ Ni, whose ground state is magnetic with S T = 3/2 and S T = 1/2, respectively, the ¹⁹F-NMR spectrum has a complicated structure which depends on the strength and orientation of the magnetic field, due to both isotropic and anisotropic transferred hyperfine interactions and classical dipolar interactions. From the 19F-NMR spectra in single crystals we estimated the transferred hyperfine constants for both the F⁻-Ni2⁺ and the F⁻-Cd2⁺ bonds. The values of the hyperfine constants compare well to the ones known for F⁻-Ni2⁺ in KNiF₃ and NiF₂ and for F⁻-Cr³⁺ in K₂NaCrF₆. The results are discussed in terms of hybridization of the 2s, 2p orbitals of the F⁻ ion and the d orbitals of the magnetic ion. Finally, we discuss the implications of our results for the electron-spin decoherence.

  3. Rapid Solidification Behavior of Fe-Cr-Mn-Mo-Si-C Alloys

    NASA Astrophysics Data System (ADS)

    Ranganathan, Sathees; Makaya, Advenit; Fredriksson, Hasse; Savage, Steven

    2007-12-01

    The rapid solidification behavior of alloys in the Fe-Cr-Mn-Mo-Si-C system was investigated for different compositions and cooling rates. The C content was varied and alloying additions of Mo and B were studied with respect to their effect on the microstructure. The alloys were cast as either melt-spun ribbons or as 1-mm-thick plates after levitation or as rods 2 to 4 mm in diameter by injection into copper molds. A homogeneous single-phase structure was obtained for the alloy of composition 72.8Fe-8Cr-6Mn-5Si-5Mo-3.2C (wt pct), for a sample diameter of 2.85 mm, at a cooling rate of ≈1100 K/s. The single-phase structure was identified as a metastable solid solution, exhibiting the characteristics of the ɛ phase. Upon reheating, decomposition of the single-phase structure into fine bainite plates and secondary carbides was observed between 600 °C and 700 °C. The annealed structure obtained showed high hardness values (>850 HV).

  4. Synthesis, structures and magnetic properties of the dimorphic Mn2CrSbO6 oxide.

    PubMed

    Dos santos-García, Antonio J; Solana-Madruga, Elena; Ritter, Clemens; Ávila-Brande, David; Fabelo, Oscar; Sáez-Puche, Regino

    2015-06-21

    The perovskite polymorph of Mn(2)CrSbO(6) compound has been synthesized at 8 GPa and 1473 K. It crystallizes in the monoclinic P21/n space group with cell parameters a = 5.2180 (2) Å, b = 5.3710(2) Å, c = 7.5874(1) Å and β = 90.36(1)°. Magnetic susceptibility and magnetization measurements show the simultaneous antiferromagnetic ordering of Mn(2+) and Cr(3+) sublattices below TN = 55 K with a small canting. Low temperature powder neutron diffraction reveals a commensurate magnetic structure with spins confined to the ac-plane and a propagation vector κ = [1/2 0 1/2]. The thermal treatment of this compound induces an irreversible phase transition to the ilmenite polymorph, which has been isolated at 973 K and crystallizes in R3[combining macron] space group with cell parameters a = 5.2084 (4) Å and c = 14.4000 (11) Å. Magnetic susceptibility, magnetization and powder neutron diffraction data confirm the antiferromagnetic helical ordering of spins in an incommensurate magnetic structure with κ = [00 0.46] below 60 K, and the temperature dependence of the propagation vector up to κ = [00 0.54] at about 10 K. PMID:25623228

  5. Microstructure and Oxidation Resistance of NiCoCrAlYTa Coating by Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Liang, X.-H.; Zhou, K. S.; Liu, M.; Hong, R. J.; Deng, C. G.; Luo, S.; Chen, Z. K.

    The NiCoCrAlYTa coating was prepared on Ni-based single crystal super-alloys by low pressure plasma spraying (LPPS). The phases and microstructures for the coatings were characterized by X-ray diffraction and scanning electron microscopy, and the fracture toughness and micro-hardness for both coatings and substrate were also investigated. The relationship between coating properties and oxidation was analyzed. The result shows that elementary distribution of NiCoCrAlYTa coatings, which consists of γ-Ni, β-NiAl, γ'-Ni3Al, and CrCoTa phases, is much homogeneous. The composition changes with depth from the surface to substrate for the coatings. The micro-hardness of coatings is 350.8 HV0.3 and fracture toughness is 2.73 MPa m1/2. The oxidation resistance of coatings excelled than Ni-based single crystal super-alloys.

  6. In operando study of the high voltage spinel cathode material LiNi(0.5)Mn(1.5)O4 using two dimensional full-field spectroscopic imaging of Ni and Mn.

    PubMed

    Bauer, Sondes; de Biasi, Lea; Glatthaar, Sven; Toukam, Leonel; Gesswein, Holger; Baumbach, Tilo

    2015-07-01

    LiNi0.5Mn1.5O4 spinel cathode was studied during the first discharge cycle using combined full field Transmission X-ray Microscopy (TXM) and X-ray Absorption Near Edge Structure Spectroscopy (XANES) techniques to follow the chemical phase transformation as well as the microstructural evolution of cathode materials upon operation within an electrochemical cell. The spatial distribution and electrochemical process of the spinel material with spherical granules of 30 μm and 3 μm crystallite size was investigated. The spectroscopic imaging of the cathode within field of view of 40 × 32 μm(2) and spatial resolution of 40 nm has revealed an increase of the LiNi0.5Mn1.5O4 granule size during lithiation providing an insight into the effect of the particle size and morphology on the electrochemical process. The chemical elemental distribution and the content of the different oxidation states of the two absorbing elements (Ni and Mn) have been determined in operando from the XANES imaging. A gradual increase in the content of the oxidation state Mn(3+) from 8% up to 64% has been recorded during the discharge from 5 V to 2.7 V. The study of the local oxidation reduction behavior of Mn(3+) reveals a reversibility aspect in the local electrochemical reaction of Mn(4+) toward Mn(3+) in areas located in the center of the aggregate as well as in areas closed to the electrolyte. During the discharge process, a mixture of Mn(3+) and Mn(4+) has been detected while only single electron valence states have been found in the case of Ni. Probing the chemical changes during the discharge using two-dimensional XANES reveals spatial differences in the electrochemical activities of the two absorbing elements Ni and Mn. PMID:26051380

  7. Experimental study and thermodynamic modeling of the Al-Co-Cr-Ni system

    NASA Astrophysics Data System (ADS)

    Gheno, Thomas; Liu, Xuan L.; Lindwall, Greta; Liu, Zi-Kui; Gleeson, Brian

    2015-10-01

    A thermodynamic database for the Al-Co-Cr-Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for the β-γ equilibrium, and good agreement for three-phase β-γ-σ and β-γ-α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.

  8. NiCrSiB Coatings Deposited by Plasma Transferred Arc on Different Steel Substrates

    NASA Astrophysics Data System (ADS)

    Reinaldo, P. R.; D'Oliveira, A. S. C. M.

    2013-02-01

    Colmonoy 6 (NiCrSiB) is a Ni-based alloy recognized for its superior mechanical properties, attributed to the presence of a dispersion of hard carbides and borides, which is strongly dependent on processing technique. This work gathered microstructure data from the literature and analyzed Colmonoy 6 coatings deposited by plasma transferred arc hardfacing. The aim of the study was to determine the influence of PTA deposition parameters and substrate chemical composition on NiCrSiB coating characteristics. Coatings were characterized in terms of their hardness, dilution, and microstructure, as well as mass loss during abrasive sliding wear tests. The results showed that coating performance is strongly dependent on the chemical composition of the substrate. Carbon steel substrate yielded coatings with greater wear resistance. Processing parameters also alter the performance of coatings, and the lower current and lower travel speed result in reduced mass loss.

  9. Formation of stable nanostructured phases in plasma-jet-treated Ni-Cr powder coatings

    NASA Astrophysics Data System (ADS)

    Alontseva, D. L.; Bratushka, S. N.; Il'yashenko, M. V.; Makhmudov, N. A.; Prokhorenkova, N. V.; Onanchenko, E. L.; Novgorodtsev, A. I.; Pshik, A. V.; Rogoz, V. N.

    2012-08-01

    Samples of steel St3 with Ni-Cr-B-Si-Fe coatings deposited using a plasma jet with subsequent partial melting of the coatings by a plasma jet have been investigated for the first time using the methods of Rutherford backscattering spectroscopy, scanning electron microscopy, X-ray fluorescence analysis, X-ray photoelectron spectroscopy, and nanoindentation. The structure and the phase and elemental compositions of these coatings have been studied. Ni-based nanocrystalline phases and CrNi3-based microcrystalline phases with crystals from 50 to 150 nm in size, extended defects of the microstructure, and nanoregions with different orientations of the crystal lattice and grain sizes on the order of 2-3 nm have been found.

  10. Radiation resistance of (Ni,Fe)Cr2O4 spinels by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Van Brutzel, Laurent; Alvarez, Pierre; Chartier, Alain

    2014-05-01

    Molecular dynamics simulations are carried out to study primary radiation damage in NiCr2O4 and FeCr2O4 spinels, which are part of the corrosion layer of the vapour generators used in nuclear reactors. The radiation resistance of both spinels is evaluated by studying point defect recombination processes, threshold displacement energies, and 20 keV displacement cascades initiated with different PKA masses. Results are mainly in agreement with previous studies involving MgAl2O4 showing that radiation facilitates the transition to inverse spinel structure or NaCl structure. However, we find some differences between the two studied spinels indicating that NiCr2O4 is more sensitive to radiation.

  11. Microstructural observations in rapidly-solidified and heat-treated Ni3Al-Cr alloys

    NASA Technical Reports Server (NTRS)

    Carro, G.; Flanagan, W. F.

    1992-01-01

    The microstructural development following heat treatments of several rapidly-solidified Ni3Al-Cr and Ni3Al-Cr-B alloys is presented. Depending on composition, the as-solidified samples were either 100 percent gamma-prime phase - in the form of fine antiphase domains (APD) - or a mixture of gamma-prime (APDs) and beta phases. Upon annealing, the as-solidified microstructures transform to either APD-free gamma-prime or mixtures of gamma and gamma-prime phases. For those compositions where the quenched microstructures were 100 percent gamma-prime it was observed that APD coarsening followed conventional grain-growth kinetics, but when gamma phase precipitated on the APD boundaries the rate constant changed abruptly while the time exponent remained unaffected. It was also found that alloys containing critical amounts of chromium and boron are susceptible to precipitation of the boride Cr5B3.

  12. Phase-Specific Elastic/Plastic Interface Interactions in Layered Cr-NiAl Structures

    SciTech Connect

    Barabash, Rozaliya; Liu, W.; Tischler, Jonathan Zachary; Bei, Hongbin; Budai, John D

    2012-01-01

    The depth-dependent, as-grown and deformation-induced strain and dislocations partitioned through the interfaces in a two-phase layered NiAl-Cr(Mo) structure are directly measured at the mesoscale using 3-D X-ray microdiffraction. It is demonstrated that in the as-grown, undeformed state, neighboring submicron Cr solid solution and NiAl eutectic lamellae (doped with {approx}3% Mo) form a heterointerface with 180{sup o} rotation around a <1 1 2> pole. It is shown that the mechanical response to the indentation of a layered composite with alternating Cr(Mo)-NiAl lamellae is distinct from the response of single-phase materials. In the center of the indent, after the load is released, the NiAl lamellae are under compressive forward stresses (with the same sign as the indentation-induced compression) while Cr solid solution lamellae are under tensile back stresses (with opposite sign from the indentation load). The depth-dependent alternation of compressive/tensile residual strains in the neighboring Cr solid solution and NiAl lamellae is understood in the framework of the Mughrabi's composite model considering two types of structure elements: harder and softer regions. Under indentation, both kinds of lamellae are assumed to deform compatibly. After the load is released, residual forward stresses are formed in the harder lamellae, and back stresses are formed in the mechanically softer lamellae. Line-broadening analysis of the intensity distribution along the diffraction vector reveals a 15-times increase in dislocation density in the near-surface zone in the center of the indent. Such a large increase is typical for severe deformation.

  13. Ti12.5Zr21V10Cr8.5MnxCo1.5Ni46.5-x AB2-type metal hydride alloys for electrochemical storage application: Part 2. Hydrogen storage and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Young, K.; Chao, B.; Bendersky, L. A.; Wang, K.

    2012-11-01

    In Part 2 of this report, the hydrogen gas charging and electrochemical properties of a series of AB2-based metal alloys (Ti12.5Zr21V10Cr8.5MnxCo1.5Ni46.5-x) designed to have different fractions of Zr-Ni-type secondary phases by varying the Mn/Ni-content were studied to establish correlations of these properties with abundances of the secondary phases. In the gas charging, the general trend of pressure-concentration-temperature slope factor and hysteresis is to diminish with increase in the Zr7Ni10 phase abundance; the trend of reversible hydrogen storage capacity is to increase as the TiNi-derived AB phase abundance increases. As for the electrochemical properties, the number of activation cycles needed to achieve a given percentage of capacity and power decreases with increase in the total amount of secondary phases. Trends of changes in both the total and reversible capacities follow that in AB phase abundance; the evolution of high-rate dischargeability, bulk diffusion, and surface exchange current is similar to that of Zr7Ni10 phase abundance - increase in the beginning and decrease afterward as the Mn-content in the alloy increases. Other properties, such as metal-hydrogen bond strength and maximum gaseous phase storage capacity, are predominately dependent on the alloys' composition, i.e. the Mn/Ni ratio.

  14. Effects of Cr, Zr, V, Mn, Fe, and Co to the hydride properties of Laves phase-related body-centered-cubic solid solution alloys

    NASA Astrophysics Data System (ADS)

    Young, K.; Ouchi, T.; Nei, J.; Meng, T.

    2015-05-01

    Chemical composition modifications of a Laves phase-related BCC solid solution base alloy, Ti15.6Zr2.1V44Cr11.2Mn6.9Fe2.7Co1.4Ni15.7Al0.3, were investigated in order to study the function of each constituent element on the structural, gaseous phase and electrochemical hydrogen storage properties of these alloys. In general, removal of Fe and decrease in V-content in exchange for higher Ni-content were found to improve both the electrochemical capacity and high-rate dischargeability, which are related to the decrease in C14-content and increase in TiNi-content. However, total elimination of the C14 phase by removal of Zr resulted in a reduced discharge capacity, a prolonged activation period, and a less catalytic surface for electrochemical reaction. Besides the BCC and C14 phases, the TiNi phase was also found in every alloy in this study, contributing positively to the bulk diffusion of hydrogen while hindering the surface electrochemical reaction.

  15. Cr-substituted Ni-Zn ferrites via oxalate decomposition. Structural, electrical and magnetic properties

    NASA Astrophysics Data System (ADS)

    Gabal, M. A.; Al Angari, Y. M.; Al-Agel, F. A.

    2015-10-01

    A series of Cr-substituted Ni-Zn ferrites; Ni0.8Zn0.2CrxFe2-xO4 (x=0.0-1.0) were prepared via oxalate decomposition route to characterize the effect of Cr-substitution on structural, magnetic and electrical properties. The prepared powders were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and transmission electron microscopy (TEM). XRD indicated single-phase cubic ferrites. The lattice parameters (aExp) exhibited a gradual decrease with increasing chromium, attributed to the smaller ionic radii of Cr3+ substituent. According to the obtained structural data, an appropriate cation distribution was suggested and fortified through FT-IR spectroscopy besides magnetic and electrical measurements. TEM image showed agglomerated cubic crystals with an average size of about 20 nm. Vibrating sample magnetometer (VSM) measurements indicated minimal hysteresis characteristic for soft magnetic material. The decrease in saturation magnetization (Ms) with Cr-substitution was discussed in view of Neel's two sub-lattice model. The change in the coercivity with Cr-content was discussed in view of estimated cation distribution and magnetization values. The obvious fall in the Curie temperature, estimated from molar susceptibility measurements, with increasing Cr-concentrations was assigned to the gradual replacement of Fe3+ ions on the octahedral sites by paramagnetic Cr3+ ions. ac-conductivity as a function of both frequency and absolute temperature exhibited a semi-conducting behavior. The decrease in conductivity with increasing Cr-content was attributed to the preferential occupation of Cr3+ ions by octahedral sites which replacing Fe3+ ions and limiting Fe2+-Fe3+ conduction.

  16. Exploring the Cr2+ doping effect on structural, vibrational and dielectric properties of Mn-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Choudhary, Pankaj; Tyagi, Tarun; Dar, M. A.; Varshney, Dinesh

    2016-05-01

    A series of Cr doped Mn-Zn ferrites with compositional formula Mn0.5Zn0.5-xCrxFe2O4 (x = 0, 0.3, 0.5) were prepared by solid-state reaction route. X-ray diffraction (XRD) analysis reveals that the samples prepared are polycrystalline cubic spinel in structure (Fd3m) with some secondary phase of α-Fe2O3. Slight variation in the lattice parameter of Cr doped Mn0.5Zn0.5Fe2O4 has been observed due to difference in ionic radii of cations. Small shift in Raman modes towards higher wave number has been observed. Further the line width decreases with the doping ions. A giant dielectric constant ~104 is observed for parent Mn0.5Zn0.5Fe2O4 which is found to decrease with increase in Cr2+ doping. Low dielectric loss is observed for Mn0.5Zn0.5Fe2O4 and improves with Cr2+ doping at Zn2+ site.

  17. Structural and compositional characterization of RF sputter-deposited Ni-Cr + Cr2O3 films

    NASA Technical Reports Server (NTRS)

    Bhushan, B.

    1980-01-01

    An RF-sputtered chrome oxide coating with metallic binders was developed. The chrome oxide coating has high-temperature capabilities and is wear resistant, and has some self-lubricating properties. A nichrome metallic binder was added in the coating to improve its ductility without significant loss in the hardness. The sputtering parameters were optimized to obtain a smooth coating with the maximum adherence. The coatings were applied using bias-sputter and sputter-deposit modes on the heat treated and annealed foil substrates. The coating applied on annealed foils using the sputter-deposit mode was smooth and had the best adherence. Metallurgical examinations showed that the coating was Ni-Cr + Cr2O3. The coating as applied was amorphous and it crystallized during substrate heat treatment.

  18. Concentration and distribution of Cr and Ni in soils of Talcahuano, Chile.

    NASA Astrophysics Data System (ADS)

    Tume, Pedro; Gonzalez, Elizabeth; King, Robert; Alvarez, Manuel; Roca, Nuria; Bech, Jaume

    2015-04-01

    Urban soils can serve as a recipient for a large amount of trace elements from multiple sources, including, municipal wastes, vehicular emissions and industrial wastes.Several researchers have pointed out the need for a better understanding of urban soils in order to assist in developing strategies to protect urban environments and human health against the longterm accumulation of trace elements.The objectives of this study were to (1) define the background levels of chromium (Cr) and nickel (Ni) in soil of Talcahuano; (2) evaluate the site contaminated by trace metals.In this study, 140 soil plots (420 samples: TS:0-10 cm; SS:10-20 cm and BS:150 cm) located approximately in a 1 km regular grid covering the Talcahuano city(94 square km) have been examined. Soil samples (<2mm fraction) were analyzed by standard methods. Aqua regia digest (ISO 11466.2002) of Cr and Ni were analyzed by Atomic Absorption Spectrophotometry. The median concentrations (mg kg-1) obtained include: Cr 134 (range 66.6 - 657) and Ni 56.1 (26.4 - 137). In weakly developed urban soils, Ni follows the same pattern without any real distinguishing features. Chromium displays slight surface enrichment (Cr content in topsoil (mg kg-1): 145±70; Cr content in basement (mg kg-1): 138 ± 53 ). However, the differences are not significative. Different methods were evaluated in order to facilitate the best diagnosis of contamination. First, the trace metal geochemical background was determined using basic descriptive statistics. The upper limit (Upper Whisker value) of the background content in mg•kg-1is 266 for Cr and 112 for Ni. Secondly, the basic descriptive statistics were then compared with Dutch guidelines, in order to evaluate whether the concentrations measured in soils were abnormally high or not. By comparing the results of the different methods, we estimate that 5% of the soils demonstrate anthropogenic signatures of Cr and Ni.The greatest enrichment anomalies in heavy metals were detected

  19. Critical evaluation of sequential leaching procedures for the determination of Ni and Mn species in welding fumes.

    PubMed

    Berlinger, B; Náray, M; Sajó, I; Záray, G

    2009-06-01

    In this work, welding fume samples were collected in a welding plant, where corrosion-resistant steel and unalloyed structural steel were welded by gas metal arc welding (GMAW) and manual metal arc welding (MMAW) techniques. The welding fumes were sampled with a fixed-point sampling strategy applying Higgins-Dewell cyclones. The following solutions were used to dissolve the different species of Ni and Mn: ammonium citrate solution [1.7% (m/v) diammonium hydrogen citrate and 0.5% (m/v) citric acid monohydrate] for 'soluble' Ni, 50:1 methanol-bromine solution for metallic Ni, 0.01 M ammonium acetate for soluble Mn, 25% acetic acid for Mn(0) and Mn(2+) and 0.5% hydroxylammonium chloride in 25% acetic acid for Mn(3+) and Mn(4+). 'Insoluble' Ni and Mn contents of the samples were determined after microwave-assisted digestion with the mixture of concentrated (cc). HNO(3), cc. HCl and cc. HF. The sample solutions were analysed by inductively coupled plasma quadrupole mass spectrometry and inductively coupled plasma atomic emission spectrometry. The levels of total Ni and Mn measured in the workplace air were different because of significant differences of the fume generation rates and the distributions of the components in the welding fumes between the welding processes. For quality control of the leaching process, dissolution of the pure stoichiometric Mn and Ni compounds and their mixtures weighing was investigated using the optimized leaching conditions. The results showed the adequacy of the procedure for the pure metal compounds. Based on the extraction procedures, the predominant oxidation states of Ni and Mn proved to be very different depending on the welding techniques and type of the welded steels. The largest amount of Mn in GMAW fumes were found as insoluble Mn (46 and 35% in case of corrosion-resistant steel and unalloyed structural steel, respectively), while MMAW fumes contain mainly soluble Mn, Mn(0) and Mn(2+) (78%) and Mn(3+) and Mn(4+) (54%) in case of

  20. Grain boundary depletion and migration during selective oxidation of Cr in a Ni-5Cr binary alloy exposed to high-temperature hydrogenated water

    SciTech Connect

    Schreiber, Daniel K.; Olszta, Matthew J.; Bruemmer, Stephen M.

    2014-10-01

    High-resolution microscopy of a high-purity Ni-5Cr alloy exposed to 360°C hydrogenated water reveals intergranular selective oxidation of Cr accompanied by local Cr depletion and diffusion-induced grain boundary migration (DIGM). The corrosion-product oxide consists of a porous, interconnected network of Cr2O3 platelets with no further O ingress into the metal ahead. Extensive grain boundary depletion of Cr (to <0.05at.%) is observed typically 20–100 nm wide as a result of DIGM and reaching depths of many micrometers beyond the oxidation front.